Conjugation is the creation of derived forms of a verb from one basic form. Conjugation may be affected by person, number, gender, tense, mood, voice, or some other language-specific factor or factors. When a verb is used to function as the action done by a subject, the verb must be conjugated in most languages.

For example, here's a sample conjugation of the English verb to be and its Latin and French equivalents, esse and être.

to be / esse / être

Form / Person	English	Latin	French
Infinitive	to be	esse	être
1st singular	I am	sum	je suis
2nd singular	you are	es	tu es
3rd singular	he, she, or it is	est	il/elle est
1st plural	we are	sumus	nous sommes
2nd plural	you are	estis	vous êtes
3rd plural	they are	sunt	ils/elles sont

Note that the similarity between English is and Latin est is not a mere coincidence, but rather one of the consequences of them having a distant common ancestor (see Indo-European languages). French is a derivative of Latin, which explains the much greater similarity in the way they conjugate this verb.

In addition, there are 4 regular conjugations, and one sub-form:

Indicative present
First conjugation -a (amare, to love) Singular 1st amo 2nd amas 3rd amat Plural 1st amamus 2nd amatis 3rd amant		Second conjugation -e (habere, to have or hold) Singular 1st habeo 2nd habes 3rd habet Plural 1st habemus 2nd habetis 3rd habent
Third conjugation -e regere (to rule) Singular 1st rego 2nd reges 3rd reget Plural 1st regemus 2nd regetis 3rd regent	Third conjugation -i- stem -i (capere, to capture) Singular 1st capio 2nd capis 3rd capit Plural 1st capimus 2nd capitis 3rd capiunt	Fourth conjugation -i (audire, to hear) Singular 1st audio 2nd audis 3rd audit Plural 1st audimus 2nd auditis 3rd audiunt

Notice in all forms the endings are similar, 'o' or 'm' endings mean I. 's' means 'you' (in the pronouns suus means his, do not get confused) and the 't' endings mean he/she/it.

So:

Singular

1. -o/m = I, eg. sum or verbo
2. -s = You, eg. es or amas
3. -t = He, eg est or amat

Plural (note the simularities with the singular)

1. -mus
2. -atis
3. -nt

Elements of conjugation survive in English, however it is watered down. 'am' (I am) retains the nasal 'mmm' sound inherited from its ancestors (note: me). 'is' is remarkably similar to the Latin 'est'.

See also: Latin declension