Why is this word plural even when referring to a single person?
This is not plural. Plural is wayyishtahawu. Singular had a supposed form like *"wayyishtahw," which immediately changed to "wayyishtahu."
Rabbi Dr. Seth Mandel
Rabbinic Coordinator
The Orthodox Union
Voice (212) 613-8330 Fax (212) 613-0718 e-mail mandels@ou.org
I'm no expert; I just "eavesdrop" on these conversations, but I think the "vav" is part of the shoresh.
The plural version is "vayishtachavu," with two vavs.
(I'm sure I'll be corrected if I'm wrong, as I should be!)
Dov (Kramer)
The real question is not what the plural IS, but why the singular looks/sounds like a plural.