[Grammar] I like grape

[beachboy]

Is it right to say "I like watermelon/watermelons/melon/melons/grape/grapes? I don't think it's right to say "I like grape". Is there a rule?

 

[teechar]

Use the plural in both cases, unless you're using the name of the fruit as an adjective.

I like apples/melons/watermelons/grapes.

I like apple/melon/watermelon/grape juice.