Disambiguations of Rishonim

Often times, two contradictory statements of a Rishon will baffle the Poskim, and all it takes is a little history to know that there were actually two or more people with the same name, each of which said one of the contradictory statements.

Rif

1. Rabbeinu Yitzchak ben Yaakov Alfasi, the Rif, had a grandson, Rav Yitzchak ben Reuven, who is known as the Baal HaShe'arim. Some Poskim weren't aware of this and mistakenly posed contradictions between the writings of the two.

Raavad

It's important to be aware that there are three individuals known as the Ra'avad:

1. R' Avraham ibn Daud of Spain, author of Sefer HaKabbalah
2. R' Avraham ben Yitzchak Av Beit Din of Narbonne, who wrote the Sefer HaEshkol
3. His son in law, and R' Avraham ben David of Posquières, author of the Hasagot on the Baal HaMaor and Rambam, Baalei HaNefesh, and quoted extensively by Rishonim.

Riva

"ריב"א" can stand for a couple of different names, or even two people of the same name, as such, it's beneficial to specify who is who.

1. R' Yitzchak HaLevi Bar Asher, probably one of Rashi's teachers.
2. R' Yitzchak Bar Asher, a student of Rashi who was named after the former and was one of the Baalei HaTosafot, also known as Riva.
3. R' Yitzchak Bar Avraham of Shantz, also known as Ritzba (ריצב"א), or Ri HaBachur, brother of the Rash MiShantz, and was killed Al Kiddush Hashem. Some say he's also the same person as the Ri HaLavan
4. R' Yitzchak Bar Abba Mari, who wrote Sefer HaIttur.

Rabbeinu Yonah

There were at least four Rabbeinu Yonahs:

1. R' Yonah Gerondi (HeChassid), whom we know as Rabbeinu Yonah, cousin of the Ramban, and Rebbe of the Rashba. His grandson, son of his daughter and the Ramban's son Shlomo, was named R' Yonah after him. He had grandson who was also named R' Yonah, whose daughter married the Rashbetz and was thereby the grandfather of the Rashbash.
2. R' Yonah שניין, a cousin of the R' Yonah Gerondi, who overlapped in his lifetime.
3. R' Yonah author of the Sefer Issur veHetter and Talmid of the Terumat HaDeshen. Printers and Poskim mistakenly labeled his Sefer as a product of R' Yonah Gerondi, but it's clearly impossible.

Rabbeinu Baruch

1. Sefer HaTerumah was written by R' Baruch MiRegensburg, the student of R' Eliezer MiMitz, R' Baruch MiMagence, who wrote Sefer HaChochmah.

Rabbeinu Zerachiah

1. There were two R' Zerachiahs, one of whom was the Baal HaMaor,, and the other was R' Zerachiah HaYevani, who wrote the Mussar work, Sefer HaYashar. He should not be confused with Rabbeinu Tam, who also wrote a Sefer HaYashar on Shas and Shu"t.

Rabbeinu Tam

Of course, Rabbeinu Tam is well known as Rashi's grandson, R' Yaakov ben Meir, but some Rishonim do refer to R' Yaakov author of Shu"t Min HaShamayim as "Rabbeinu Tam," as well.

Ri

1. There were two Ri Baalei HaTosafots, one of whom was the Ri, Rav Yitzchak Bar Shmuel HaZaken, nephew of Rabbeinu Tam through his sister. The other is the Ri HaLavan or Ri HaBachur mentioned above (see Riva).

R' Asher (Rosh)

1. The Rosh quoted by the Baal HaTerumot, Mordechai, Hagahot Maimoniot, and Kol Bo is Rabbi Asher MiLunell, not Rabbi Asher Ben Yechiel of Toledo, as the latter lived much later.

Riaz

"ריא"ז" can stand for a number of names:

1. Rav Yitzchak Ohr Zarua
2. R' Yeshaya HaAcharon, commonly known as Riaz

Rambam

There were a number of people named Rabbeinu Moshe ben Maimon throughout the generations.

1. The Rambam
2. Rav Moshe ben Maimono "Cordobi," a contemporary of the Rambam who also lived in Cordova.
3. Rambam "al Fasi," who lived later.
4. Rav Moshe ben Maimon "Elbaz"

Ran

1. The Ran quoted by the Orchot Chaim is someone named R' Natan, not R' Nissim ben Reuven of Gerona.