Pronunciation / Pronouncing the letter "s"

A1 Breakthrough
The sound  /s/ is well known in many languages. It's the second most frequenty used consonant in French, after the sound /ʀ/.
It has a twin which is the sound /z/.
The sound  /z/ is pronounced the same way: the air continually goes between the front of the tongue and the upper teeth, the tongue stays
down. Moreover, the vocal cords vibrate during the whole sound emission. To easily pronounce the sound /z/, keep the tip of the tongue against your lower teeth and make sure you keep your vocal cords vibrating from the beginning to the end. Feel the vibration with two fingers pressed on your throat. It's easier to say /z/ in words which contain /g/ (to keep your tongue down) and /m/ (to make your vocal cords vibrate). We can also think about to the sound bees and mosquitoes make: zzzzz This twin comes in ninth place in terms of frequency but it is very important to stress the plural: - marking the plural with the liaison between determiners and nouns that begin with a vowel:  les_oiseaux - marking the verbs plural:  ils_ , elles_ before a verb beginning with a vowel:  il aime / ils_aiment, elle ouvre / elles_ouvrent, il apporte / ils_apportent, … It's also the feminine mark of the adjectives in the masculine form ending with the letters "-s", "-x":  compris, heureux, nombreux, français
The difference between /s/ and /z/ enables to distinguish  Ils sont (être) / ils_ont (avoir)
In general, the letter "s" is pronounced /s/: -in words beginning (Strasbourg, siège) -before a consonant (historique, cosmopolite) - in words ending (un sens). In the middle of a word between two vowels, there are two possibilities as in the well known pairs: poisson / poison, dessert/ désert. The "ss" between two vowels spelling indicates the pronunciation /s /.