- It is forbidden from the Torah for a man to seclude himself with a woman to whom he is forbidden. It is Rabbinically forbidden for a man to seclude himself with any woman, even a single woman. It doesn't matter if the woman is Jewish or non-Jewish.
Multiple Men and Women
- It is permitted for many men and women to be secluded together. What constitutes many men and many women? Some poskim write that only if there's 3 men and 3 women , some say 2 men and 3 women, and some say 2 men and 2 women constitute many men and many women. The poskim are general strict to consider it 3 men and 3 women.
- According to Sephardim, one man may not be secluded with multiple woman and one woman may not be secluded with multiple men. 
- It is permitted for a man to seclude himself with his mother, daughter, granddaughter, or wife even when she in her state of Niddah. It is permissible for a man to seclude himself with his sister, however, it shouldn't be done frequently.  A brother and sister still living in their parents home may be left alone together for only a few days and not for an extended period of time. 
- Yichud with two sisters is forbidden. Some say that yichud with a mother and her daughter or grandmother and her granddaughter or grandson is permitted.
Husband in the City
- If a woman's husband is in the city, it's permissible to seclude with her unless one has a close relationship with her (Libo Gas Ba) such as if one grew up with her or is a relative. 
- What is considered a close relationship such that there is no leniency of having one's husband in the city? Some say that even a professional acquaintance is considered a close relationship, while others limit it to a step-sibling or a relative.
- Some poskim hold that this only applies if the husband can come at any moment but not if a person knows that their husband isn't coming home until a certain time since he's at work or is involved with a specific task. Others are lenient.
Wife Protecting Husband
- When one’s wife is with him, there is no problem of being alone with other women as well. This only applies if one's wife is in the same room with him but not if one's wife is just in the same city.
Mother, Daughter, or Sister Breaking Yichud
- Most poskim assume that this leniency of having a very close relative such as one's wife isn't yichud and protects from yichud, applies also to one's mother, daughter, and sister as well. Therefore, if a man is in a room with his wife, mother, daughter or sister, and one other woman he does not violate the yichud prohibition.  Similarly, the minhag is to permit yichud for a grandchild with one's grandmother. Then even if there's another woman there it isn't yichud because of the presence of the grandmother.
Open to the Public
- It is permitted for a man and woman to be secluded with one another in an area that is open to the public except at nighttime. Nighttime is defined by when people aren't traveling the streets.
- A door open to the street permits yichud even with a non-Jew or someone who is suspect to immorality.
- A door open to the street only permits that room and not rooms connected to it on other floors or even other rooms on that same floor.
- An apartment that opens to a courtyard inhabited by three people or more, or someone who would prevent yichud such as a couple, if the door is open to that courtyard that is considered like being open to the public domain. If someone knows that the neighbors aren't going to enter one's house the door actually would have to be open and not closed but unlocked according to all opinions.
Closed But Unlocked
- Some say that as long as the door is unlocked even if it is closed that area is considered open to the public, however, some say that it is only considered open if the door is actually open. Practically, some say that one can be lenient only if people in that area enter without knocking and getting permission. Some say that in cases of need one can be lenient regarding any rabbinical form of yichud.
- According to those who hold that it is permitted to have yichud in a house that's closed but unlocked some say that the same is true with a house that is locked but others who would break yichud have the keys and can enter at any time.
A Woman One Is Comfortable With
- Some poskim hold that it is forbidden to seclude oneself with a woman which one is comfortable around in an area open to the public, while others permit it. 
Windows to the Street
- If there is a window that makes the room visible from the street someone who is in front of that window is considered as though it is open to the public and there's no yichud. One condition for this to be applicable is that the window needs to be low enough that people from the street can easily see into the room normally. There are some poskim who hold that if the window is high enough that a person from the street could see in while walking on his tippy toes that is also considered open to the public, while others disagree.
- There are poskim who significantly limit the applicability of this leniency so that it is almost irrelevant. They explain that if the room has a corner or a place in it which isn't visible from the street through that window then the window isn't considered open to the public since there's a concern that a person will walk away from the window into the secluded area of that room. Furthermore, some poskim say that if the room which has a window is connected to another room that isn't open to the public then again there is no leniency by having a window the public since it is easy to walk away from the window into the other room. Yet some poskim disagree with these last two conditions and hold that a window to the public permits yichud while one is visible to the public.
- Some say that it is forbidden for a man and woman to seclude themselves together even if there's a camera or webcam that makes everything in the room visible to onlookers in another location.  If someone is monitoring the camera, ome poskim say that one can be lenient. 
- According to Sephardim, if on the road at that time there's on average a car every 3 minutes and it is possible to see inside the car then there's no yichud for a man and woman together in a car. If the road isn't heavily traveled it is forbidden unless there are three men and three women, such as on a bus. However, on a bus where there was three men and three women and then some of them leave, if a woman is left alone with a male driver the woman must exit the bus unless there is a danger to get off. 
- According to Ashkenazim, some say that it is not proper for a man and woman to travel alone in a car, while many others say that it is only forbidden to travel alone on small streets, where there only a few cars on the road.
- It is permissible for a man to enter an elevator with a woman because the time in travel is usually very short. Some say that it is permitted if the elevator has a travel time of less than 3 minutes. 
- Many authorities hold that one man may not be in the same house as a woman even if they are in different rooms. 
- If a woman locks herself in a room and the man in on the outside room that is considered yichud.
Doctor and Patient
- For a dentist/doctor, yichud may be permitted if one is caught up in his work to the point that he will not do anything inappropriate. This leniency doesn't apply if the patient is the doctor's last patient unless there is a secretary or someone else in the office who is waiting for the doctor to come out of the room. Some do not like this heter alone for yichud.
- A second potential heter for yichud for a dentist/doctor is that he/she will receive professional repercussions if he/she would act inappropriately. This suffices as a preventative measure.
- A third way to avoid yichud is by ensuring that other individuals can see inside the room or by simply making sure others are present.
- If when a dentist sees a patient he/she closes the door, if others commonly walk in, it could be muttar. But if other people never walk in when the door is closed, it would be assur.
- The relationship between a dentist/patient can be transformed into a libo gas ba situation if they develop a relationship through the professional interactions. Then these heteirim would not apply.
- The minhag is to permit a man to teach girls if he's married even if his wife isn't in the same city.
- A woman can be a teacher for boys if her husband is in the town all the time (so that no issue of yichud arises).
- ↑ Shulchan Aruch EH 22:1-2, Aruch Hashulchan EH 22:1, Kitzur Shulchan Aruch 152:1, Yalkut Yosef Hilchot Ishut EH Siman 22:1-2.
- The Gemara Kiddushin 80b and Avoda Zara 36b learns from a Pasuk that Yichud with a relative who one is forbidden to live with (someone who would be in the category of Arayot) is prohibited. The Gemara (Avoda Zara 36b) explicitly calls Yichud with a married women to be a biblical prohibition. Thus, Tur EH 22:1 writes that Yichud with an Erveh is biblical. The Rambam (Issurei Biyah 22:2), however, argues that Yichud is only Divrei Kabbalah. Bet Yosef (EH 22:1) explains that the Rambam holds that the gemara's expression that Yichud is biblical only meant that it is hinted to in the Torah.
- The Perisha EH 22 posits that there's a biblical prohibition to have yichud with someone who is forbidden on a Biblical level (lav). Chazon Ish EH 34:6 agrees.
- The Gemara Avoda Zara 36b says that the Bet Din of Dovid HaMelech instituted the prohibition of Yichud with a single woman and Bet Shamai and Bet Hillel extended Yichud to a non-Jewish woman as well.
- Does the prohibition of yichud include a concern of rape or just seduction? Igrot Moshe 4:65:19 writes that yichud was instituted for seduction or mutual consent and not rape.
- Is there a concern that if a man and woman currently aren't in a state of yichud that they will move into a state of yichud such as with a car since they might drive to a deserted alley? Igrot Moshe EH 4:65:2-3 is concerned for this. He says that this seems to be the dispute between Rabbenu Yerucham and Maharshal in Bet Shmuel 22:9 and we follow the Maharshal.
- ↑ Shulchan Aruch EH 22:6
- ↑ Birkei Yosef EH 22:3, Pitchei Teshuva 22:5, Chelkat Mechokek EH 22:6 quotes this idea from the Maggid Mishna but questions it.
- ↑ Bet Shmuel 22:8, Chaye Adam 126:3
- ↑ Bach 22
- ↑ Igrot Moshe EH 4:65:15
- ↑ Yalkut Yosef Hilchot Ishut EH Siman 22:10. According to Yam Shel Shlomo Kiddushin Siman 20 and Sh"t Maharsham 3:152, one man with two women is a biblical prohibition. See however, Sh"t HaRashba 1:587 and Sh"t Chavot Yair 73
- ↑ Yalkut Yosef Hilchot Ishut EH Siman 22:1, Gan Naul pages 9-10. Igrot Moshe EH 4:64 writes that the exact amount of time isn't critical, it is only permitted if they're only there as a guest in a very evident way and not living there for some period of time.
- ↑ Gan Naul pages 10-12. See Igrot Moshe EH 4:65:11 concludes that this depends on the particular situation.
- ↑ Igrot Moshe EH 4:64 at the end
- ↑ Shulchan Aruch EH 22:7, Yalkut Yosef Hilchot Ishut EH Siman 22:7
- ↑ Aruch Hashulchan EH 22:6 held that a professional acquaintance is considered libo gas ba but the Tzitz Eliezer 40:12:2 disagreed and quotes the Chida in Shaar Yosef 3 who is lenient.
- ↑ Igrot Moshe EH 4:65:6
- ↑ Yalkut Yosef EH 22:7 is lenient even if the husband is on the other side of town or he doesn't know in where his wife currently is.
- ↑ Shulchan Aruch Even Haezer 22:5. Beit Shmuel 22:8 says that the reason for this leniency is that one’s wife is assumed to watch him to avoid sinning.
- ↑ Igrot Moshe EH 4:65:5
- ↑ The Pitchei Teshuva EH 22:2 does not extend this Heter to one’s daughter (meaning a man, his daughter and another woman would violate Yichud), while Iggerot Moshe Even Haezer 2:15 extends it to a daughter and in Iggerot Moshe 4:65:8 extends it to a mother, and sister as well. The Nitei Gavriel Yichud 40:1 follows Rav Moshe (and in footnote 1 quotes many others who do as well).
- ↑ Rav Soloveitchik as cited in Nefesh Harav p. 256 was lenient about a man with his grandmother even though there was another one of his female cousins there since the man with his grandmother isn't yichud and the grandmother protects him from yichud with another woman.
Rav Schachter comments that this is in accordance with Igrot Moshe EH 2:15.
- ↑ Kiddushin 81a, Shulchan Aruch EH 22:9
- ↑ Beer Heitev 22:9, Kitzur Shulchan Aruch 152:5. Igrot Moshe EH 4:65:5 is strict and writes that even in a big city practically there's no case that one can assume that there's a concern of someone entering all hours of the night.
- ↑ Dvar Halacha 3:14 quotes the Knesset Hagedola and others that the definition of night for public depends on when people are traveling the streets. He cites the Chazon Ish who said that in Bnei Brak he ruled until 10pm it is considered open to the public.
- ↑ Chida in Birkei Yosef 22:9 and Shaar Yosef 3. Dvar Halacha 3:17 agrees. Otzar Haposkim 22:9:11 cites this Chida and no one else on the issue.
- ↑ Knesset Hagedolah (Hagahot Tur EH 22:11) writes that a door that's open to the street only permits that room and not the upper or lower floors connected to that room. The Otzar Haposkim 22:9:5 quotes the Apei Zutrei 22:20 and Nichpeh Bkesef who agree.
- ↑ The Otzar Haposkim 22:9:5 quotes the Nidrei Zerizin 2:9 and Bet Shlomo OC 48 who write that rooms connected to a room open to the public are still subject to yichud, only the room that is open to the public itself is permitted. On the other hand, the Ezer Mkodesh seems to be lenient. Dvar Halacha 3:9 quotes this dispute and adds that the Bet Meir is strict but the Maharsham is lenient.
- ↑ Dvar Halacha 3:5
- ↑ Rashba (responsa 1:1251)
- ↑ Pitchei Teshuva 22:8 quoting the Beit Meir and Rabbi Akiva Eiger (responsa 100)
- ↑ Nitai Gavriel (Yichud 33:1), Dvar Halacha (responsa 26). See Igrot Moshe EH 4:65:4 who is lenient regarding yichud in a room with the door unlocked to the public since almost everyone would answer the door if someone knocked and he's afraid of someone entering unless it is locked. He adds that this is only applicable if generally people would enter the house without permission if it is unlocked.
- ↑ Rabbi Uri Orlian in a shiur on yutorah.org (min 70-3)
- ↑ Dvar Halacha 3:3 quoting the Chazon Ish
- ↑ The Chelkat Mechokek 22:13 writes that a person who is comfortable around a certain woman is forbidden to seclude himself with her in an area open to the public. The Taz 22:9, however, disagrees and permits. Chida (Birkei Yosef 22:6 and Birkei Yosef 245:6) proves from Shulchan Aruch and others that it is permitted but he isn't willing to be lenient. Kitzur Shulchan Aruch 152:5 rules like the Chelkat Mechokek. Misgeret Hashulchan 152:10 cited by Otzar Haposkim 22:9:13 is lenient in extenuating circumstances. Nitai Gavriel (Yichud 32:7) writes that in cases of need such as with a doctor one may be lenient unless the person is comfortable around the woman in an inappropriate sense. Tzitz Eliezer 6:40:12:4-8 is lenient. Gan Naul 8:25 seems to be lenient. He quotes the Shevet Halevi 5:23:7 and Divrei Chachamim 5:11 as permitting, while the Nodeh Beyehuda EH 2:18, Aruch Hashulchan 22:6, and Igrot Moshe EH 4:60 are strict.
- ↑ The Nodeh Beyehuda 1:71 writes that a window that is visible to the public is considered like the room is open to the public and there's no yichud. Otzar Haposkim 22:9:4 quotes the Maharsham Introduction to 2:76 who is lenient if you the window is high but can be seen from another house if someone in that other house were to stand on a chair, however, he isn't lenient with the same situation in the street. Gan Naul 8:18 rules like the Maharsham. Tzitz Eliezer 6:40:11:8 holds that a window permits yichud even if it is only possible to see in from the public while standing on one's tippy toes. Igrot Moshe EH 4:65:2 seems like he is only lenient with a window if you can be seen normally and not that a person needs to get on his tippy toes. However, the Gan Naul ch.
8 fnt. 59 explains Igrot Moshe in accordance with the Maharsham.
- ↑ The Ezer Mkodesh 22:9 (cited by Otzar Haposkim 22:9:4) writes that if the room which the window is open to has a corner or secluded area which isn't visible from the window then the window doesn't permit anything since there's a concern that the man and woman will walk into that secluded area. The Bet Yitzchak Glick 3:220:2 and Misgeret Hashulchan 52:10 quote this.
- ↑ Igrot Moshe EH 4:65:2 writes that if the room in which there's a window is open to another room that isn't open to the public then yichud is prohibited even in front of the window. See the previous footnote for the explanation.
- ↑ Gan Naul 8:16 proves from the Nodeh Beyehuda and others that there is no concern that someone who is currently not in a state of yichud will enter into a state of yichud. As such he writes that standing in front of the window that is visible to the public undoes yichud even if it is easily possible to walk into a secluded area. Gan Naul quotes Rav Elyashiv as being lenient on a window in the room even if there are secluded parts of the room as long as one is in front of the window. Dvar Halacha 3:13 agreed.
- ↑ Kuntres Internet BeHalacha (p. 33) discusses whether having a webcam is similar to having a door open to the public domain and in the conclusion quotes Rav Elyashiv saying that it is not a valid leniency.
- ↑ yichud with video-camera. They also write that it is possible that it is also permissible if it is recording, even if nobody is watching. see also Rabbi Eli Mansour DailyHalacha. Rabbi Aryeh Lebowitz in a Ten Minute Halacha explained that it seems that a security camera that can be monitored at any time is enough to prevent yichud.
- ↑ Yalkut Yosef Hilchot Ishut EH Siman 22:9, Gan Naul 8:22. Gan Naul cites Rav Meir Mazuz in Or Torah 18:108:37 as agreeing.
- Rav Moshe in Sh”t Igrot Moshe EH 4:65:3 writes that initially it is not proper for a man and woman to travel alone because of a concern that they may stop in a deserted area and do something inappropriate. However, in a case of pressing need such as if a woman in the community needs to go to the same place he’s traveling and if he refuses he’ll be considered selfish, one may rely on those who hold that there’s no concern that they will stop in a deserted area. He compares this to a discussion in the Bet Shmuel 22:9.
- However, Rav Shlomo Zalman in Minchat Shlomo 1:91(21) writes that sometimes there's room to be lenient to rely on the fact that the car has windows which are visible to the public and that there's no concern that they may stop in a deserted place. (See there for more details). Additionally, Rav Vosner in Shevet HaLevi 5:202(1) writes that regarding the nighttime concern, there's room to be lenient since the person driving can't fall asleep, however, he adds that since sometimes intercity highways or even local streets become deserted at night one should be strict.
- Lastly, Rabbi Jachter quotes Rav Mordechai Eliyahu (cited in Techumin 10:311), Rav Aharon Lichtenstein, and Rav Mordechai Willig as ruling that it is permitted for a man to travel alone in a car with a woman unless they are driving in a very remote area or at a time when there are very few cars on the road. Nitei Gavriel (Yichud 44:1) rules that one roads where cars continue to pass by and the roads are well lit, there's no Yichud, however, on small streets where not very many cars travel it's forbidden. See further Rabbi Mansour on DailyHalacha.com.
- ↑ Rabbi Jachter quoting Teshuvot Igrot Moshe E.H. 4:65:16, Teshuvot Tzitz Eliezer 6:40:22, and Rav Shlomo Zalman Auerbach (Minchat Shlomo 1:91:22) say that it is permitted for a man to enter an elevator with a woman and it isn't yichud.
- ↑ Yalkut Yosef (Chinuch pg 389), Gan Naul 8:21. Rav Orlian mentions that potentially going up the glass elevators in CN towers in Toronto which are taller than 1100 ft and the elevators take 58 seconds is a bit of a question of yichud if a man and woman go in together.
- ↑ Sh"t Igrot Moshe 4:65:19. Rabbi Aryeh Lebowitz explains that even though Rav Moshe is strict there are some are opinions who are lenient but does not give a final ruling. See also Salmat Chaim 151, Chazon Ish 34:1-2, Shaar HaTziyun 239:27, Chachmat Adam 126:7, Divrei Malkiel 4:22, Tzitz Eliezer 6:40 (chap 7:10).
- ↑ Igrot Moshe EH 4:65:19
- ↑ Igros Moshe (E”H 4:65:1) says that a male OBGYN is so caught up in his work that he will not have any bad desires. He continues that even after he completed seeing the patient and other patients are waiting and he is not necessarily busy with the work at this moment, he doesn’t have time to linger around and must rush to the next patient, so there is no potential issur that he will do in that short time span. If it is the end of the day and no more patients are coming, he can rely on the secretary or someone else in the building to mitigate the issur yichud.
- ↑ Rav Shlomo Zalman Auerbach quoted in Nishmat Avraham 3:9 quotes the Gemara Kiddushin 80b which says that yichud applies even to a man and woman who are burying a baby in a cemetery, showing that there is an issur yichud even when one is busy with something where theoretically there should be no yetzer hara.
- ↑ The Otzar Haposkim 22:8:7 quotes the Yaskil Avdi 2:17, Tzitz Eliezer 6:40:12:8. Nishmat Avraham as quoted by Rabbi Mordechai Torczyner. Tzitz Eliezer says that this heter may potentially only apply when both individuals involved are busy with the work. In a dentist/patient relationship, only the dentist is preoccupied, so the heter may not apply. See Chazon Ish EH 35:2 regarding this approach.
- ↑ Igros Moshe E”H 4:65:2 says that if a window is low enough for people outside to see, there is no yichud. But if the window is very high to the point that the people outside must climb up a ladder to see inside, which is very unnatural, that would be an issur yichud. When it comes to a dentist/patient, if they are visible to the public through a window, that can potentially avoid yichud.
- ↑ Rav Moshe Shternbuch says that if one goes to a dentist/doctor of the opposite gender, one should bring his/her spouse or another relative.
- ↑ Rav Shlomo Zalman Auerbach
- ↑ Rav Shlomo Zalman Auerbach, quoted in Nishmat Avraham 3:94-95
- ↑ Igrot Moshe EH 4:65:13 writes that the minhag is to follow Rabbi Akiva Eiger and not the Chelkat Mechokek 22:21 on this question.
- ↑ Igrot Moshe EH 4:65:18