The Present Simple Tense

I, you, we, they, the Simple Present tense uses the base form of the verb – V1
An example: V1 of the verb “to work” = work – You work.
When the subject is he, she, it, the Simple Present tense uses the base form of the verb with the addition of -s/-es – V1 + s/es
An example: He works.

person you work
3rd person he/she/it works

Plural
1st person we work
2nd person you work
3rd person they work

boils at 100 degrees Centigrade.
2. A permanent situation
An example: She works in this office.
3. Habits or things that are regularly done.
An example: They play chess every Monday.

not + V1 (+ object).
With a third person singular subject (he, she, it) we must use does.
With all other subjects we must use do.
Examples: This student does not study French.
These students do not study French.