Liaison: when liaison takes place
In careful colloquial speech, liaison takes place:
- between the article and the noun or the following adjective: un ami, les amis
- between a pronominal adjective and the following noun or adjective: certains enfants
- between adjective and noun: grand homme, grand effort
- between the personal pronouns and the following verbs : nous avons, ils ont
- between verbs and personal pronouns in interrogative form: ont-ils?
- usually between auxiliary verbs and participe passé in the forms of compound tenses: nous avons aimé (but not as, auras, eusses)
- between the prepositions and the following word: chez un ami, dans aucun cas (but not after the preposition vers)
- between an adverb and a word it defines, especially when the adverb is très, bien, tout
- in many ossified expressions.
There are even more liaisons in the solemn pronunciation.
However, one cannot use liaison:
- after et: et un
- after vers: vers elle
- before h aspirated : les haches
- before un, huit, onze.