Explainer / Tanakh
Isaiah 7:14
Therefore the Lord himself will give you a sign: behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel.
לָכֵן יִתֵּן אֲדֹנָי הוּא לָכֶם אוֹת הִנֵּה הָעַלְמָה הָרָה וְיֹלֶדֶת בֵּן וְקָרָאת שְׁמוֹ עִמָּנוּ אֵל
We kept the ASV's wording, in modern English, including "virgin."
Why
עַלְמָה
means a young woman of marriageable age.
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It is used of Rebekah before her marriage (Gen 24:43), of Miriam as a girl (Exod 2:8), and of maidens at court (Ps 68:25; Song 6:8). The word does not by itself specify virginity, though an unmarried עַלְמָה would ordinarily be one.
בְּתוּלָה
is the more specific Hebrew word for "virgin" (Gen 24:16; Deut 22:19).
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Isaiah does not use it here.
The Septuagint
rendered עַלְמָה here as παρθένος, "virgin," about two centuries before Yeshua.
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Matthew quotes the verse in that Greek form (Matt 1:23), and this version keeps "virgin" in Isaiah to match.
עִמָּנוּ אֵל, "Immanuel,"
is "with us is God," a name made of a short sentence, like the names of Isaiah's sons (8:3, 8:18).
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Matthew gives its meaning as "God with us."
"a virgin" (ASV, ESV, NASB); "a young woman" (RSV, NRSV).