The Mishna says the earliest time for shema is from when the kohanim eat their trumah. The gemara explains why it didn't say from tzeit hakochavim.
But throughout the entire second daf, we find different time periods for the earliest time for shema:
When the poor eats his bread
When everyone eats on erev shabbos
When the day becomes sanctified on shabbos etc.
Why does the gemara use these "codewords" to say the earliest time for shema?
Dov Gelman, Pittsburgh, US
Sholom Rav.
The Mishnah gives the earliest time for Keri'as Sh'ma as when the Kohanim arrive home to eat their Terumah, which is synonymous with Tzeis ha'Kochavim.
The Beraisa on Amud Beis gives a variety of different times than the Mishnah, and it discusses whether some of them do or don't coincide with Tzeis ha'Kochavavim and whether they do or don't coincide with one another.
Be'VIrchas Kol Tuv.
Eliezer Chrysler