vegetable和fruit可数吗?书上有个句子是eating more vegetables and fruit is good for your health.为什么vegetable用了复数,而fruit用的单数呢?

fruit 作水果解释的时候,既是可数名词,又是不可数名词.作果实解释的时候是可数名词.但在中文里的确不好分辩.具体叙述是不可数,如果指好几种不同类的水果可以用复数.（参考people的用法）
e.g.
Apples,oranges,strawberries are kinds of fruit/are all fruit.苹果,橙子,草莓是几种水果/都是水果.
The potato is a vegetable,not a fruit.土豆是蔬菜,不是水果.
The drink is made from four tropical fruits.这种饮料是四种热带水果做成的.
参考资料：Longman Dictionary of Contemporary English