Pronunciation / The French "h"

The French "h" is a silent letter that is not pronounced. However, in the beginning of the word (handicap) and in a word like "dehors,"
"Tahiti," "Sahara," the "h" allows or prevents the combination of the consonant and vowel to form a syllable. 
The "h" that allows the consonant-vowel combination is called the "silent h" and the "h" that prevents this is called the "aspirated h."
 
The "silent h" is not pronounced and allows elisions, liaisons and catenation.
 

The silent "h"

 
Elision
Liaison
Catenation (linking vowels from word to word)
NOUNS
L'hôpital
Un_homme, des_hommes
Cet_hôpital
ADJECTIVES

L'horrible accident
C'est très_humain

Quel_horrible accident !
VERBS
 
Je m'habille.
 
Ils habitent au Vietnam.
 
Il hésite à aller aux urgences.
 

The aspirated "h" is not pronounced and prevents elision, or omission (see: Pronunciation / Elision and deletion), liaison (see: Pronunciation / Liaison) and catenation (see: Pronunciation / Catenation (linking vowels from word to word)).
 

The aspirated "h"

 
No elision
No liaison
No catenation
NOUNS
La // hauteur
Les // héros
Le handicapé
ADJECTIVES
C'est le // huitième étage.
Les // hautes études
Une // haute fonction
VERBS
Je // hurle.
Ils // hurlent.
Il // harcèle.


There is no rule to distinguish words that have an "aspirated h" from words that have a "silent h." The only explanation comes from etymology. The "silent h" comes from Latin and is often found in languages of Latin origin. The "aspirated h" comes from words borrowed from other languages like English (le hall), Frankish (le haricot), Arab (le hasard) and Dutch (le hareng)...

 

The most frequent words

 
The silent "h"
The aspirated "h"
Masculine nouns
Un habitant, un hiver, un homme,
un hôpital, un horaire, un hôtel
Le Hollandais, le Hongrois, le haricot,
le hasard, le huit, le héros, le handicapé
Feminine nouns
Une habitante, une habitude, une heure
une histoire, l'humidité, l'hygiène
La Hollandaise, la Hongroise, la hanche
la hauteur, la handicapée, la hi-fi,la honte
Adjectives
Horrible, humain
Le huitième (étage)
Verbs
Habiller, habiter, hésiter
Harceler, hurler