Whilst looking up a definition I came across this sentance as a definition for ちゃんと

まちがいなく。

Ok, I get まちがい, But I can't figure out what なく means. Is it something like ない？
Rikaichan doesn't help much, and just suggests it means to cry or sing, which I assume isn't the meaning here...

I'ved tried searching but couldn't find anything so...could anyone be nice enough to enlighten me?

You can turn any i-adjective into an adverb by replacing い with く. Eg, 白い, 白く.
In this case, the whole sentence 間違いない was turned into an adverb 間違いなく. 'Mistakelessly'.

iSoron Wrote:You can turn any i-adjective into an adverb by replacing い with く. Eg, 白い, 白く.
In this case, the whole sentence 間違いない was turned into an adverb 間違いなく. 'Mistakelessly'.

I second this. Especially since ちゃんと itself seems to be an adverb.

Ah thank you! That would make a lot of sense!

If the sentance was positive however, how could you turn it into an adverb?

bombpersons Wrote:Ah thank you! That would make a lot of sense!

If the sentance was positive however, how could you turn it into an adverb?

Depends on what you were trying to say I guess. I'm not a grammar expert, in fact, I'm a total noob, but I believe that まちがい is a noun and ない turns it into an adjective ( -like being). This is why it can be turned into a adverb by changing it to なく.

If まちがいない were positive it would be something like まちがいがある.

http://www.guidetojapanese.org/surunaru.html

"Using 「なる」 and 「する」 with verbs"

States you can't modify a verb with a verb.

But you could probably add ように to make it more descriptive than stative ( I think that's the word).

まちがいがたくさんあるように彼が早くノートを書き直した。

I don't know the context, but I would say it means "without"
eg: ちゃんと間違いなく書いてください
”please write it properly without mistakes"

edit: I guess that's what iSoron was saying

まちがい (mistake) is a noun derived from the verb まちがう (to err), just like はなし (story) is derived from はなす (speak) or ほり (ditch) is derived from ほる (dig).

ない (to not exist) is the plain negative form of the verb ある (to exist). Plain negative verb forms conjugate like adjectives.
ある　　　ない　　　present
あった　　なかった　past
あって　　なくて　　て form
あり　　　ー　　　　noun form
ー　　　　なく　　　adverbial form

The expression まちがいない literally means there is no mistake. I'm not sure how it's used as an expression in practice.

まちがいなく is just the adverbial form of the expression so it would literally mean "without any mistake, having no mistakes". This makes sense since ちゃんと is an adverb meaning "perfectly, properly, exactly". In other words, something done ちゃんと is done without any mistakes.

Raichu Wrote:The expression まちがいない literally means there is no mistake. I'm not sure how it's used as an expression in practice.

間違いない、彼が行きました。
(There's no doubt, he's the one who went.)

This is just a sentence I made up, but that's how it's used in daily conversation.

I hear 間違いない all the time.

あいつだ！間違いねぇぞ！
or
間違いねぇ。あいつだ！
or countless other uses of it.