Bekhorot 36: words to know

עֵד מִפִּי עֵד (ed mi-pi ed): hearsay testimony from another witness. The Gemara discusses whether hearsay testimony is admissible to permit a blemished firstborn animal.
הַפֶּה שֶׁאָסַר (ha-peh she-asar): the mouth that prohibited [is the mouth that permitted]. The Gemara questions whether a priest's admission is believed based on this evidentiary principle.
מָה לוֹ לְשַׁקֵּר (mah lo leshaker): why would he lie; a credibility inference. The Gemara evaluates whether this principle grants credibility in an instance of mere suspicion.
דַּעֲבִידָא לְאִיגַּלּוֹיֵי (da'avida le'igaluyei): that is destined to be revealed. The Gemara explains that people do not lie about matters that can easily be discovered.
מוּמִין מוּבְהָקִין (mumin muvhakin): clear-cut and obvious blemishes. Rava qualifies that three laymen can only permit an animal with unmistakable blemishes.