1、定义：表示经常发生或习惯性的动作、状态。句中通常有usually，often，every day，sometimes，always，at weekends，on Sundays等表示经常性时间的短语。
如：I am a student.
He is Jim‟s father.
They are from Japan.
如：I often watch TV at the weekends.
Mr Green and Mrs Green like collecting stamps.
如：Jim usually visits his grandparents on Sundays.
She sometimes goes to the park with her mother.
① 一般情况下，直接加s 如：read-reads，swim-swims
② 以s，x，sh，ch，o结尾，加es 如：wash-washes，watch-watches，do-does
③ 以辅音字母＋y结尾，变y为i，再加es 如：study-studies，fly-flies
④ 不规则变化 如：have-has
|They watch TV every day.||They don’t watch TV every day.||—Do they watch TV every day? —Yes, they do. / No, they don’t.|
|She watches TV every day.||She doesn’t watch TV every day.||
— Does she watch TV every day? —Yes, she does. / No, she doesn’t.