כוס

Hebrew

Root
כ־ו־ס (k-w-s)

כּוֹס • (kos) f or m (plural indefinite כּוֹסוֹת, singular construct כּוֹס־, plural construct כּוֹסוֹת־)

Like other words that start with ב,‎ ג,‎ ד,‎ כ,‎ פ,‎ or ת, this term's initial letter takes a dagesh lene. In older texts, that dagesh is usually dropped when the word is preceded, in the same phrase, by a word ending in a mater lectionis; in modern texts, the dagesh is usually preserved even in such a case. Likewise, in older texts, the dagesh is always dropped when the word is prefixed by an indefinite ב־‏,‎ כ־‏,‎ or ל־‏, or by ו־‏; in modern speech, the dagesh is often preserved in such a case. (After the definite ב־‏,‎ כ־‏,‎ and ל־‏, and after the prefixes ה־‏,‎ מ־‏,‎ and ש־‏, there is a dagesh forte, as described in the usage notes for those prefixes.)
This noun is feminine in the Bible, but is masculine in the Mishnah and in later writings, even to modern times. When Hebrew was revived as a spoken language, though, the word reverted to feminine, as in the Bible.

Declension of כּוֹס

Root
כ־ו־ס (k-w-s)

From Proto-Semitic *kôs (“owl”), which has been cited as a possible source for the name of the Greek island Κῶς (Kôs).^[1]

כּוֹס • (kos) m

From Arabic كُس (kus), from Persian (kos, “cunt”).

כּוּס • (kus) m

^ Bernal, M. (2020). Black Athena: The Afroasiatic Roots of Classical Civilation Volume III: The Linguistic Evidence. United States: Rutgers University Press.