Of course it is. It's a little wrong
to say a tomato is a VEGETABLE.
The Big Bang Theory Season 2, Episode 20
Dried potatoes, VEGETABLE oil,
The Big Bang Theory Season 5, Episode 24
...and refers to a lantern
hand-carved from a root VEGETABLE...
The Big Bang Theory Season 3, Episode 15
The world's most boring liquid
and the world's most boring VEGETABLE,
The Big Bang Theory Season 10, Episode 13
and one large VEGETABLE.
The Big Bang Theory Season 12, Episode 19