fruit表示“水果”时,通常用作总称或集体名词,不可数.
如：He just lived on fruit.他只靠吃水果维持生命.Would you like some more fruit?
你要不要再吃点水果?若表示水果种类,则是可数的.
如：The mango is a tropical fruit.芒果是种热带水果.The tree bears a red hard fruit.
这种树结一种红色坚硬的`果实.但有时到底是表示总称还是种类,完全取决于具体的语境,有时两种情况都说得通.
如：The country exports tropical fruit(s).该国出口热带水果.
fruit表示“几种（多种、各种）水果”时,可直接说some(many,various)fruits,也可用some(many,various) kinds of fruit（后者通常用不用复数）.
如：Some [Some kinds of] fruits don’t freeze well at all.有些水果根本就不能冷藏.
They sell various [various kinds of] fruits at that shop.那个商店卖各种水果