Rendezvous
The silent letter in the word "RENDEZVOUS" is the letter "Z." In French, the word "rendezvous" means a meeting or gathering, and the "Z" is silent in the pronunciation of the word. The silent "Z" is a common feature in French words borrowed into English, where the pronunciation has evolved but the spelling has remained intact.
The word "hello" has no Z in it.
Knit
Nah, the "z" isn't silent, because the vowel stress doesn't go in the next vowel after the z. If the word was "zdràveite", i.e. if the vowel stress gone into the first "a", then the z had to be silent. But since the word is "zdravèite" and the stress goes into the first e, the z is not silent. So, the word "zdraveite" is properly read as [zdra'vejte].
silent
Silent means very quiet, so any words that mean "quiet" can be modified to mean silent. Other options are hushed, noiseless, or soundless.
pizazz
buzzbuzzarddazzledrizzledizzyfizzfuzzfuzzyfizzlefrazzledguzzlegizzardgrizzlyjazzmuzzlenozzlenuzzlepuzzlepizzarazzsizzlewhizzed
Yes
No, "silent" is not an onomatopoeia. Onomatopoeia refers to words that imitate natural sounds, such as "buzz," "meow," or "click." "Silent" does not imitate any sound.
sword
There are not any letters z in this sentence, but there are two places where you pronounce /z/: words and friends. You pronounce them as /z/ because d is a voiced sound.