答：這要看你想表達什么了.如要問：怎么回事,怎么啦?則應說：What's the matter?=What's wrong?
如果將matter看成抽象的名詞,表示“物質(zhì)”（與精神相對者）,問：什么是物質(zhì)?
則What's matter?也是正確的句子.這一點大多數(shù) 人想不到的.
查詞典：
2 [U]
(a) physical substance in
general (contrasted with mind or spirit) 物質(zhì)（與精神相對）
inert matter 無生命的物質(zhì)
to study the
properties of matter 研究物質(zhì)的特性.
The universe is composed of matter.宇宙是由物質(zhì)組成的.
比如最后一個例句,接下去問：那么什么是物質(zhì)呢?就可以說：Then what is matter?
回答可以是：
Matter is something that occupies space and can be perceived by one or more senses;
Matter is a physical body,a physical substance,or the universe as a whole.
物質(zhì)：占據(jù)一定空間并能被一種或多種感覺感知到的東西；實體、物質(zhì)或整個宇宙
樓主又沒有限定這句話一定是要表達“怎么了?出什么問題了?”,為什么思想僵化,大家就一致認為：What's matter?是錯句呢?