The English word “half” can be translated into French in several different ways depending on context. French does not use a single equivalent word for all situations. The most common translations include demi, moitié, mi- as a prefix, and partie in some contexts.

Demi

The word demi is often used as an adjective placed before a noun to mean “half of” something. When placed before a noun, demi does not agree in gender or number. When placed after a noun with un(e), it agrees and usually takes the form demie.

• “Un demi-kilo de pommes”
  “A half-kilo of apples”
• “Une demi-heure”
  “A half hour”
• “Un demi-sommeil”
  “A half-sleep”
• “Une heure et demie”
  “One and a half hours”

Moitié

The word moitié is used as a noun meaning “half” or “a half portion”. It is often used with the definite article la moitié de.

• “La moitié du gâteau”
  “Half of the cake”
• “Il a mangé la moitié de son sandwich”
  “He ate half of his sandwich”
• “La moitié des élèves est absente”
  “Half of the students are absent”
• “Nous avons parcouru la moitié du chemin”
  “We covered half of the way”

Mi- as a prefix

The prefix mi- is sometimes attached to adjectives or nouns to suggest something that is halfway between two states.

• “Une expression mi-figue mi-raisin”
  “An expression half-fig, half-grape” (meaning ambiguous or mixed)
• “Un ton mi-sérieux mi-amusé”
  “A tone half serious, half amused”
• “Une chambre mi-salon mi-bureau”
  “A room half living room, half office”

Partie

In certain contexts, especially when talking about a portion of something divided, French may use partie to express “half”.

• “La première partie du film”
  “The first half of the film”
• “Il a joué une partie du match”
  “He played half of the match”
• “Cette partie du travail est terminée”
  “This half of the work is finished”