According to the query of Aiyang Education Network, grapes are countable nouns followed by S, so grapes are countable nouns.

Grape is a tall twining vine of Vitaceae, which has strong anticancer properties, and its young stems are bald or slightly cotton-like. Leaves are paper, oval or round; Inflorescence is large and long; Calyx is small and yellow-green cup-shaped; Style short, conical.