Grammar - 第三人称单数 Third Person Singular
语法要点
什么是第三人称单数
he、she、it，以及一个人或一个东西的名字（如 Tom、My mother、The dog），说的都是"一个人/一个东西"，这些叫第三人称单数。
He likes apples.
She plays tennis.
It runs fast.
Tom goes to school.
基本规则：动词要加 s
表示平时经常做的事情，如果主语是 he、she、it 或一个人/一个东西，后面的动词通常要加 s。
I play football. → He plays football.
I like apples. → She likes apples.
They run every day. → Tom runs every day.
I read books. → My mother reads books.
大多数动词直接加 s
大部分动词只要在词尾直接加 s，就变成第三人称单数形式。
play → plays — He plays basketball.
eat → eats — The cat eats fish.
drink → drinks — She drinks milk.
read → reads — He reads a book every night.
以 s/x/ch/sh/o 结尾加 es
以 s、x、ch、sh、o 结尾的动词，通常要加 es，而不是只加 s。
go → goes — She goes to school.
do → does — He does his homework.
watch → watches — He watches cartoons.
wash → washes — Mum washes the dishes.
辅音字母 + y，变 y 为 i 再加 es
动词以"辅音字母 + y"结尾时，要把 y 变成 i，再加 es；如果 y 前面是元音字母，直接加 s 就行。
study → studies — He studies English every day.
fly → flies — The bird flies in the sky.
carry → carries — She carries a big bag.
play → plays — He plays football. (y 前面是元音 a，直接加 s)
特殊变化：have → has
有几个常用动词的第三人称单数形式不是简单加 s，需要单独记住，其中 have 变成 has 最特殊。
She has a cat.
He does his homework every day.
Tom goes to school by bus.
否定句：doesn't + 动词原形
表示"他/她/它不......"时，用 does not（缩写 doesn't）加动词原形；因为 doesn't 已经带走了 s，后面的动词不能再加 s。
He doesn't like apples.
She doesn't play football.
Tom doesn't eat meat.
The dog doesn't run fast.
疑问句：Does + 主语 + 动词原形
问"他/她/它......吗？"时，把 Does 放到句子最前面，后面的动词用原形；回答用 Yes, ... does. / No, ... doesn't.
Does he like apples? — Yes, he does.
Does she play tennis? — No, she doesn't.
Does Tom go to school by bus?
Does the dog eat meat?
Do 还是 Does？
I、you、we、they 用 do；he、she、it（以及一个人/一个东西）用 does。
Do you like cats?
Do they play football?
Does he like cats?
Does she read books?
容易搞错的地方
He play football.（❌ 错误）
He 是第三人称单数，动词后面忘了加 s
❌ He play football every day.
He plays football.（✅ 正确）
第三人称单数主语后面的动词要加 s
✅ He plays football every day.
Does she likes cats?（❌ 错误）
前面已经有 Does，后面动词又加了 s，多此一举
❌ Does he plays basketball?
Does she like cats?（✅ 正确）
Does 出现后，后面的动词要用原形，不能再加 s
✅ Does he play basketball?
Tom doesn't goes to school.（❌ 错误）
有了 doesn't，后面又给动词加了 s，重复了
❌ She doesn't likes apples.
Tom doesn't go to school.（✅ 正确）
doesn't 已经带走了第三人称单数的 s，动词要用原形
✅ She doesn't like apples.
He haves a cat.（❌ 错误）
have 的第三人称单数不是简单加 s，不能写成 haves
❌ She haves a dog.
He has a cat.（✅ 正确）
have 的特殊变化是 has，要单独记住
✅ She has a dog.
总结
第三人称单数指 he / she / it / 一个人或一个东西（如 Tom、My mother、The dog）
肯定句：he/she/it + 动词加 s 或 es（study→studies, go→goes, have→has）
否定句：he/she/it + doesn't + 动词原形
疑问句：Does + he/she/it + 动词原形 ...?
超级口诀：He, She, It，动词后面加 s！Does / doesn't 一出现，后面动词变原形！