In the English language how do verbs forms their plural and singular forms?

In English the conjugation of verbs in the singular and plural depends on the 'person' that is used.

For example
Present Tense of run, (regular verb)
Singular:
1st person: I run
2nd person You run
3rd person: He, she, it (John, Mary, the car engine etc) runs.

Plural:
1st person: We run
2nd person You run
3rd person: They run

You can see that, for regular verbs, only the verb form for the 3rd person singular changes, usually by adding -s.

Spelling of 3rd person singular for particular word endings:
Verbs ending with consonant + y: change the y to i and add -es, e.g. cry -> cries
Verbs ending with -s, -z, -ch, -sh, -x: add -es, e.g. watch -> watches
Exceptions:
have -> has
go -> goes
do -> does
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IRREGULAR VERBS
Verb forms for the plural and singular present tense of most irregular verbs follow the same rules as above, with the notable exception of 'to be', which has its own rules:
Singular
1st person: I am
2nd person: You are
3rd person: He/she/it (John, Mary, the sky etc) is

Plural
1st person: We are
2nd person: You are
3rd person: They are
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NOTE
The past and future tense form for regular and most irregular verbs does not change for singular or plural.
e.g.
Past: I ran, you ran, he ran, she ran, they ran, we all ran!
Future: I (you, he, she, it, we, they) will run.

Exception: 'to be'
Singular: I was, you were, he/she/it was
Plural: We (you, they) were
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