Isaiah 7, behold, a virgin shall conceive and bear a son, Immanuel, coming disaster.

The greek Septuagint translation: παρθένος, parthenos: a maiden, a virgin

The Hebrew word  הָעַלְמָ֗ה hā-‘al-māh, is properly translated virgin, but it can also mean a young woman, which in those days meant the same thing, age is of no importance, virginity is.