Jastrow: מ"ם

מ"ם, מֵם Mem, name of the thirteenth letter of the alphabet. Sabb. 103ᵇ מ"ם דשם סתומה Ms. O. (ed. סתום) the Mem in shem is closed (final letter); מ"ם שמעון פתוחה (ed. פתוח) the Mem in Shimʿon is open (initial letter). Ib. 104ᵃ מ"ם פתוחה מ"ם סתומה מאמר וכ׳ the open and the closed Mems intimate that there are subjects in the Law which are open to all, and such as are closed (esoteric studies). Y. Meg. I, 71ᵈ מהו דין דכתיב מ"ם מ"ם וכ׳ why is it that the letters Mem, Nun &c. are written in two ways?—Maas. Sh. IV, 11; a. fr.—Pl. מֵמִין, מֵימִין. Sabb. 103ᵃ one must not write מ׳ סמכין וכ׳ Mem like Samekh or vice versa; a. e.