I am a bit confused about these two words

değil  and değildir

I know değil means not but what and where does the other word means and used for?

please help

thanks in advance

I think değildir is used in official or formal text to emphasise it. The dir at the end means ´is´ so it´s like saying .............IS (definitely) NOT .......

 Ah ... that is way I only see it on signs.

Thanks sonunda

değil, değildirden pek farklı değildir

(sorry, I am just bored )

good one

now i remember "müdür müdür müdür?"

 i liked it .

sometimes "değildir" used for guess in negative sentences, you are not 100% sure but you think it is not.

Hey, bak, şu Ahmet değil mi? (Hey, look, is that Ahmet?)

Zannetmiyorum, değildir. (I don´t think so, he is not Ahmet)