Isaiah 7:14 - Ellicott's Commentary On The Whole Bible

Behold, a virgin shall conceive, and bear a son... — Better, behold, the young woman, or perhaps the bride, shall conceive. The first noun has the definite article in the Hebrew, and the word, though commonly used of the unmarried, strictly speaking denotes rather one who has arrived at marriageable age. “Bride,” in the old English and German sense of the word as applied to one who is about to become a wife, or is still a young wife, will, perhaps, best express its relation to the two Hebrew words which respectively and distinctively are used for “virgin” and for “wife.” In Psalms 68:26, the Authorised Version gives “damsels.” The mysterious prophecy which was thus delivered to Ahaz has been very differently interpreted.