And I feel it is necessary for me to point out that the Septuagint (Greek OT), which actually predates the Tanakh (used now for Hebrew OT), makes the virginity of Mary more clear.
See
this, also:
" Whereas “almah” is translated in the KJV as “virgin” and this rendering is supported from the Greek Septuagint translation, Jewish revisers and naturalistic textual critics prefer to render “almah” as “young woman,” hoping to undercut the prophetic value of the passage. They claim that if Isaiah were really desiring to prophesy that a virgin would conceive, that he would have used the Hebrew word “bethulah”, which is claimed as a more proper word for “virgin”…“almah” is in fact a more proper term to denote virginity in Hebrew. Further, its translation by early Jewish scholars into the Greek Septuagint demonstrates that the idea of virginity was understood to be conveyed in Isaiah 7:14 and that in pre-Christian Judaism, there was no problem identifying the “almah” of Isaiah 7:14 as being virginal in her conception."
Re: Use of the Hebrew word “almah” in prophetic Scripture. I think the most obvious reason why we know the passage in Isaiah 7:14 really meant “virgin” and not simply “young woman” is that God, speaking through the prophet Isaiah, said it was to be a SIGN unto them. What possible significance could a young woman being with child have as a sign???