Liaison
The letters s, x, z, t, d, n and m, normally silent when at the end of a word, are often pronounced when the next word begins with a vowel.
Liaison with the letters s, x, and z...
with the letters t and d..
As already mentioned, h is silent. The words beginning with h that are of latin origin act as if they begin with a vowel and liaison occurs. However, the words beginning with h that are of non-latin origin act as if they begin with a consonant - liason does not occur.
When liaison occurs with the letters n and m, they are pronounced and the vowel is denasalized.
Elision
With elision the opposite of liaison occurs - sounds normally pronounced become silent. The vowel sound of these short one syllable words all go silent before a vowel or mute h:je me te se le la de ne que jusque
French orthography marks elision by replacing the vowel with an apostrophe and combining the words.
The word si is elided only before the masculine pronouns il and ils. The word quelque is elided only before un.