כִּי

From LSJ

Εἰ θνητὸς εἶ, βέλτιστε, θνητὰ καὶ φρόνει → Mortalis quum sis, intra mortalem sape → Bist sterblich du, mein Bester, denk auch Sterbliches

Menander, Monostichoi, 173

English (Strong)

a primitive particle (the full form of the prepositional prefix) indicating causal relations of all kinds, antecedent or consequent; (by implication) very widely used as a relative conjunction or adverb (as below); often largely modified by other particles annexed: and, + (forasmuch, inasmuch, where-)as, assured(-ly), + but, certainly, doubtless, + else, even, + except, for, how, (because, in, so, than) that, + nevertheless, now, rightly, seeing, since, surely, then, therefore, + (al-)though, + till, truly, + until, when, whether, while, whom, yea, yet.
from כָּוָה; a brand or scar: burning.