The state of not getting enough food, or enough of the right food, so that the body becomes weak and unhealthy. This is the noun for the condition — the thing itself, rather than a description of a person. So a person is undernourished; what they suffer from is undernourishment. Because it names a condition rather than an event, it is uncountable: you talk about undernourishment in a region, widespread undernourishment, the effects of undernourishment. You will almost only meet it in formal writing — health reports, United Nations statistics, news about famine and poverty. It is not a word people use in conversation; if a friend asked why a child was so weak, you would say 'he isn't getting enough to eat', not 'he suffers from undernourishment'. Note the difference from 'hunger', which can mean the feeling, and from 'malnutrition', which is the more usual medical term and covers a wider problem — too little food, but also badly balanced food. In practice 'malnutrition' is far more common than 'undernourishment'; the two overlap heavily, and organisations that measure world food supply often use 'undernourishment' specifically for not getting enough calories.

營養不良（此為名詞，指這個狀態本身）