Since bechor is only male, shouldn't the plural of bechor be bechorim? The mesechta and also makas bechoros seems to be in the feminine form. Also taanis bechorim I've seen in the masculine form, so it seems we are also not being consistent. What's going on?
Max Weiman, St. Louis, USA
You are asking a good question. We do find irregular nouns which are masculine but have feminine endings and vice-versa. An example of this is the word "Lailah," which is masculine ("ha'Lailah ha'Zeh," and as we say, "Lailah Tov"), but the plural of which is "Leilos." In the same way, "Bechor" may well be masculine ("Kol ha'Bechor Asher Yivaled," Devarim 15:19), yet the plural is "Bechoros."
Regarding your second question, the Gemara in Chulin 137b asks the same question on the word "Recheilim" (lambs), which appears there in the Mishnah and which ought to be "Recheilos," since it refers to female lambs, and that is what people call them. The Gemara answers that even though people call them "Recheilos," the Torah calls them "Recheilim," so that is what the Tana calls them.
Similarly, in our case, we can say that Chazal refer to Makas Bechoros using the Lashon of the Torah (as Chazal do in numerous locations, even in connection with people; See Nechemyah 10:37). "Ta'anis Bechorim," on the other hand, is Lashon Bnei Adam, and presumably we call it by that name because it is only the male firstborns who have adopted the Minhag to fast.
Wishing you a Chag Kasher v'Same'ach,