Answer:
The following are the three different forms (masculine, feminine, plural) of every possessive noun:

my: mon, ma, mes
your (informal): ton, ta, tes
his/her/its: son, sa, ses
our: notre, notre, nos
your (formal): votre, votre, vos
their: leur, leur, leurs

For examples:
C'est ma gomme. (gomme is a feminine noun, so you use the feminine form of "my.")
Regard son crayon. (crayon is masculine, so you use son.)
Ce sont leurs poissons. (poissons is plural, so use the plural possessive form.)

Anything beginning with a vowel is preceeded by the masculine form of the possessive noun. Examples:
Allons sortir avec mon amie! (amie begins with a vowel, so use mon.)
Est-ce que tu aimes ton oncle? (oncle begins with an o, so you use ton.)

To write something as that of something/someone else, use de. For examples:
C'est le fille de Thomas. (the daughter of Thomas)
J'aime le canari de Loïc. (the yellow bird of Loïc)

Always use liaison with mon, ton, and son and with all plural forms.
For examples:
mon école (pronounce mo-nay-cohl)
nos amis (pronounce no-za-mee)
First answer by Franc 91. Last edit by Anovia. Contributor trust: 514 [recommend contributor recommended]. Question popularity: 2 [recommend question].