food作为食品的统称时为不可数名词，单数形式，指“一种食品时”可数，可以用复数。比如I like all kinds of foods, vegitables, fruits。而foods指各种食品。
拓展资料
food
1、[U] 食物
things that people or animals eat
a shortage of food/food shortages
粮食短缺
food and drink
饮食
the food industry
食品工业
2、[C, U] （某种）食物
a particular type of food
Do you like Italian food?
你喜欢意大利食物吗？
frozen foods
冷冻食品
a can of dog food (= for a dog to eat)
一罐狗食
He's off his food (= he does not want to eat anything) .
他不想吃东西。
foods
1、N-MASS 食物;食品
Food is what people and animals eat.
Enjoy your food.
用餐愉快。
2、PHRASE (常指因生病)不想吃东西，厌食
If you are off your food, you do not want to eat, usually because you are ill.
It's not like you to be off your food.
胃口不好，这可不像你了。
3、PHRASE 引人深思;发人深省
If you give someone food for thought, you make them think carefully about something.
Lord Fraser's speech offers much food for thought...
弗雷泽勋爵的讲演发人深省。