FROM STRONG’S GREEK DICTIONARY (1890)

Strong’s Greek Dictionary (1890) — public domain, printed whole.

heos ἕως — heh'-oce — of uncertain affinity; a conjunction, preposition and adverb of continuance, until (of time and place):--even (until, unto), (as) far (as), how long, (un-)til(-l), (hither-, un-, up) to, while(-s).