Possessive Adjectives- Laura K. Lawless

	Singular				Plural
English	Masculine	Feminine	Before vowel
my	mon	ma	mon		mes
your (tu form)	ton	ta	ton		tes
his, her, its	son	sa	son		ses
our	notre	notre	notre		nos
your (vous form)	votre	votre	votre		vos
their	leur	leur	leur		leurs

1. In French grammar, there are many more possessives than English, because there are different forms not only for the person and number, but sometimes also the gender and the first letter of the thing possessed.

2. When describing two or more nouns in French, a possessive adjective must be used in front of each one:

   son frère et sa sœur
   his brother and sister

   ma tante et mon oncle
   my aunt and uncle

3. The possessive adjective is almost never used with body parts in French. You can't say "my hand" or "my hair." Instead, the French use pronominal verbs to show possession with body parts:

   Je me suis cassé la jambe.
   I broke my leg (literally, I broke the leg of myself).

   Il se lave les cheveux.
   He's washing his hair (literally, He's washing the hair of himself).

In French grammar, there are three forms of the possessive for each singular person (I, you, he/she/it). The gender, number, and first letter of the noun possessed determine which form to use.

MY  

   mon (masculine singular) mon stylo > my pen
   ma (feminine singular) ma montre > my watch
   mes (plural) mes livres > my books

When a feminine noun begins with a vowel, the masculine possessive adjective is used, to avoid saying ma amie, which would break the flow of speech.

In this case, the possessive's final consonant is pronounced (the "n" in the example below) to achieve fluid pronunciation.

   mon amie - my (female) friend

YOUR (TU  FORM)

   ton (masculine singular)  ton stylo > your pen
   ta (feminine singular)  ta montre > your watch
   tes (plural)  tes livres > your books

When a feminine noun begins with a vowel, the masculine possessive adjective is used:

   ton amie - your (female) friend

Lesson: tu vs. vous

HIS / HER / ITS

   son (masculine singular)  son stylo > his, her, its pen
   sa (feminine singular)  sa montre > his, her, its watch
   ses (plural)  ses livres > his, her, its books

When a feminine noun begins with a vowel, the masculine possessive adjective is used:

   son amie - his, her, its (female) friend

Note: An important difference between French and English is that in French it is the gender of the noun that determines which form to use, not the gender of the subject.

A man would say mon livre when talking about a book, and a woman would also say mon livre. The book is masculine, and therefore so is the possessive adjective, no matter who the book belongs to. Likewise, both men and women would say ma maison, because "house" is feminine in French. It doesn't matter whether the owner of the house is male or female.

This difference between English and French possessive adjectives can be particularly confusing when talking about him/her/it. Son, sa, and ses can each mean his, her, or its depending on the context. For example, son lit can mean his bed, her bed, or its bed (for example, the dog's). If you need to stress the gender of the person the item belongs to, you can use à lui ("belonging to him") or à elle("belonging to her"):

   C'est son livre, à elle.  It's her book.

   Voici sa monnaie, à lui.  Here's his change.
 

For plural subjects (we, you, and they), French possessive adjectives are far simpler. There are only two forms for each grammatical person: singular and plural.

OUR

   notre (singular)  notre stylo > our pen
   nos (plural)  nos montres > our watches

YOUR (VOUS  FORM)

  votre (singular)  votre stylo > your pen
   vos (plural)  vos montres > your watches

Lesson: Tu vs. vous

THEIR

   leur (singular)  leur stylo > their pen
   leurs (plural)  leurs montres > their watches
 

Source-

https://www.thoughtco.com/french-possessive-adjectives-1368798