PARTS OF THE BODY
DEFINITE ARTICLES VS. POSSESSIVE ADJECTIVES

French uses definite articles (le, la, l', les) as well as possessive adjectives
(mon, ton, etc.) to qualify parts of the body, where English only uses possessive
adjectives. The difficulty resides in knowing when to use one or the other in French.

to copy explanation
A. If the part of the body is the subject of the verb, French uses a
possessive adjective:

Example: Ses cheveux tombent en cascade.

But: The French avoid using the possessive adjective as subject of the
verb "être," preferring to make the body part the object of "avoir"
(see B4 and B5 below):

Example:
1) Her hair is black = Elle a les cheuveux noirs.
2) Her feet are cold = Elle a froid aux pieds.

B. If the body part is the object of the verb or of a preposition
the possessive adjective is replaced with a definite article, if it is
clear to whom the body part belongs. This occurs:

1. when the body part is the direct object of a non-pronominal verb and this
verb expresses a common or typical action that the subject performs with
his or her own body:

Examples:
1) Elle a haussé les épaules;
2) Il tend (serre) la main;
3) Nous avons élevé la voix.

See also:
hocher la tête; cligner de l'oeil; baisser/lever les yeux,
la tête, etc; élever la voix; perdre la tête; montrer du
doigt; avancer le pied; recouvrir la vue;

But: If the action is not common or typical, French prefers the
possessive adjective:

Examples:
1) Elle a posé sa tête sur le lit.
2) Il a mis son doigt sur sa bouche.

2. when the body part is the direct object of a pronominal verb and the
reflexive pronoun clearly expresses whose body is being acted upon:

Examples:
1) Tu t'es coupé le doigt;
2) Elle s'est brossé les cheuveux.

See also:
se casser le bras (etc.); se brûler le doigt (etc.);
se couper les ongles (etc.); se peigner les cheveux;
se tordre la cheville; se faire mal au genou.

Note: The pronominal pronoun here is an indirect object. As a result,
the past particle does not agree with it.

3. when another indirect object indicates whose body part is in question
and when the action is being performed by someone else:

Examples:
1) Elle lui a tiré les cheveux.
2) Le docteur a soigné le bras de Pierre.

4. when the body part is the object of the preposition "à" in
expressions that signify sensations, such as "avoir chaud à" and
"avoir mal à":

Examples:
1) Il a froid aux mains;
2) Nous avons mal à l'estomac.

5. when the body part is the direct object of the verb "avoir" and
constitutes a physical or mental description of the subject:

Examples:
1) Les hommes ont les yeux bruns;
2) Pierre a les bras musclés.
3) Nous avons l'esprit large.

Note 1: English speakers would say "His arms are strong,"
making the body part the subject of the sentence.
French could say "Les bras de Pierre sont musclés,"
but it strongly prefers to make the body part
the direct object: "Il a les bras musclés."

But: a) When the adjective precedes the verb or when the description is
unusual or unexpected, French uses the indefinite article:

Examples:
1) Tu as de beaux yeux.
2) Elle a des épaules larges et musclés.

b) When the body part follows a verb other than "avoir" and is
qualified by an adjective (other than "droit" or "gauche"), French
uses the possessive adjective:

Examples:
1) J'ai pris sa main froide.
Mais: 2) J'ai la main froide. Il lui a pris la main droite

6. when the body part is in apposition to the verb. The resulting
phrase is translated in English by "with":

Examples:
1) Elle est arrivée, un pistolet au poing. ("with a pistol in his hands")
2) Il est parti, l'oeil fixé sur son camarade.

Note: when clothes are in apposition to the verb,
they are also preceeded by the definite article:

Examples:
1) Elle est partie, le chapeau sur la tête.
2) Il passait, les gants aux mains.

C. If an object (rather than a person) possesses something,
the latter is preceded by the definite article and "en" is
placed before the verb:

Examples:
1) J'adore cette robe, mais la couleur en est trop claire.
2) J'aime Paris et j'en connais tous les quartiers.