cousin = kuzen
nephew,  niece  = yeğen
What does “ cousin” mean in English and Turkish.Its definition?
What does “nephew: neice” mean in English and Turkish.Its definition?
Some people say there is not “cousin” in Turkish.This is a French word.

 Did you want this translated or are you asking the question to us ?

question...

 Cousin =  the son or daughter of your uncle or aunt

Nephew/ niece = the daughter or son of your sister or brother

Teşekkür ederim, Anna...

and that´s same in Turkish.

Kuzen is a loan word from French but now it is widely used, you cannot say it does not exist in Turkish. Probably nobody used it 100 years ago, though.

(I checked now from tdk and dil derneği as well. Surprisingly tdk says " Erkek yeğen." [nephew] for "kuzen", which is wrong  I think they just wrote the meaning in French [I don´t speak French]. But dil derneği, which is better in my opinion, says "Teyze, dayı, hala ya da amcanın erkek çocuğu.". It is very very very strange that they both define it male, because it is used by everyone for both female or male cousins!)

Teşekkürler...

 ... or of your husband/wife´s sister or brother

 I am surprised sonunda let this one through - she must be on holiday in Turkey!!

It is niece not neice. There is a simple rhyme to help: "I before E except after C" i.e. the i comes first, except when it is "cei" as in receive.

This should be added to the ´Something I must get off my chest thread´   

(the rest of the rhyme says ´if the sound be ee´ so a word like ´heir´ is an exception)

PS-yilgun had spelt it both correctly and incorrectly in the same post.