Hebrew grammar question

[rhu]

Shabbat is feminine; Yom (and therefore Yom Tov) is masculine. Right? So why do many (but not all) siddurim, in the מי שברך לחולים, offer

יוֹם טוֹב הִיא

rather than

יוֹם טוֹב הוּא

as the counterpart to

שַׁבָּת הִיא

?

Comments

[hatam-soferet.livejournal.com]

The husband says a) mistake or b) sometimes "yom" works as feminine, but he can't think of an example right now.

[hatam-soferet.livejournal.com]

but you could try sounding out margavriel or boroparkpyro, they both get awfully excited about that sort of thing.