Bekhorot 18: words to know

אֶפְשָׁר לְצַמְצֵם (efshar letzamtzem): it is possible to be exact or simultaneous. Used to debate whether two events or measurements can coincide precisely.
מַאי לָאו (mai lav): is it not so?. Used to propose an interpretation of the tannaitic dispute.
סֵיפָא (seifa): the latter clause of a text. Rabbi Yoḥanan cites the end of the mishna to explain Rabbi Akiva's view.
הַמּוֹצִיא מֵחֲבֵירוֹ עָלָיו הָרְאָיָה (hamotzi mechavero alav hare'ayah): the burden of proof rests on the claimant. Rabbi Akiva applies this fundamental legal principle to an uncertain firstborn.
קָא מַשְׁמַע לַן (ka mashma lan): it teaches us. Concludes why an Amoraic clarification was necessary despite being seemingly obvious.