為何noun/what後既字要加s?

當用 Present simple tense, subject (主語) 是 Third person singular (第三身單數), main verb (主動詞) 要加 –s.
如果 verb ends in -o, –s, –ch, -sh, -x 要加 –es, (wash ~ washes, fix ~ fixes)
如果 verb ends –y, y前面不是 vowel, 刪除-y, 加-ies, fly (verb) ~ flies

第三身單數包括 he, she, it, Peter, Mary, a thing (一事物), ….etc
Abstract noun, uncountable noun, noun phrase 多數是屬于第三身單數

Love is blind. Truth hurts. (Love 和 Truth 是 abstract nouns)
Chocolate tastes good. Money talks. (Chocolate 和 Money 是 uncountable nouns)
Fixing up old cars is his hobby. (Fixing up old cars 是 noun phrase)

有些字雖然 end in –s, 但是屬于第三身單數
News spreads like wild fire. (Present simple tense)
Mathematics is a difficult subject.

Nobody 是 pronoun, nobody = no one, 屬于第三身單數
Nobody knows.
Nobody is perfect.

Nobody 還可以做 countable noun, singular (plural form 是 nobodies)

Who 是 pronoun, 是單數, 指某一個人
Who cares? Who knows her?
如果用 linking verb, 要看 complement.
Who are those people? (People 是 plural)

如果 Feel 無 subject 多數指自己或你, 不用加-s
Feel like to sleep.
Please feel free to make suggestions.

What 做 pronoun, 多數 singular, 但可以 plural, 要看整句意思
What upsets me most is his arrogance. (singular ~ His arrogance upsets me)
What goes up must come down. ( singular ~ implies a thing)
What are required are faith and confidence, and willingness to work. (plural)

係第三身單數動詞後要加s。