Why is there a liaison with "comment allez-vous" and not with "comment est-il"?
Good question! I never really asked myself "why!" There IS liason with aller, avoir but not with être; perhaps because it could be confused with "tête?" I'll see if I can find a "rule" for that!
Mme
P.S. Although I did find a rule about after "adverbs" (comment...) it did not seem to be crystal clear. For that reason, I asked l'Académie Française and am awaiting clarification.
Mme
In French, a liaison occurs when a silent final consonant at the end of a word is pronounced when followed by a word that starts with a vowel sound. It is used to link words together and make the speech flow smoothly.
The reason why there is a liaison in "comment allez-vous" and not in "comment est-il" is because of the specific rules that govern liaison in French.
In the phrase "comment allez-vous," the word "allez" ends with a silent -z, and it is followed by the word "vous," which starts with a vowel sound. According to the rules of liaison, when a verb like "allez" is conjugated in the second person plural ("vous" form) and is followed by a pronoun or noun starting with a vowel sound, a liaison is made by pronouncing the normally silent -z at the end of the verb. So, "allez-vous" is pronounced as "al-lez-vous," with a pronounced -z sound.
On the other hand, in the phrase "comment est-il," the word "est" ends with a silent -t, and it is followed by the pronoun "il." However, the word "il" begins with a consonant sound. In this case, liaison is not made because there is no vowel sound following the silent final consonant -t of "est."
So, the presence or absence of a liaison in a specific phrase depends on the specific rules and the sounds of the words involved. It's important to keep in mind that liaisons are part of the pronunciation rules in French, and they vary depending on the context and the words being used.