"It is dirty."

Translation: 汚いです。

[fufulord]

汚いです

[--Monalisa--]

汚いです（kitanai desu）

[lilmndesdes]

「きたないです」 does that not mean "It is not dirty" because of the ない?

[sora_Japan]

'きたない' is 'dirty'.
'きたなくない' is 'not dirty'

Don't worry, Duo is correct. ( ´ ▽ ` ) But I understand your feeling. Certainly.

[Chris319610]

If you look at the Kanji, きたない = きたな+い = 汚+い=汚い, not きた+ない

[sora_Japan]

送り仮名/おくりがな/okurigana is ambiguous a bit. (･･;) both are used.

[V2Blast]

きたない is simply a non-negative adjective meaning "dirty". It's not related to the ない used for negation.

[hurryupanddie]

Why not "これは汚い"?

[Krynge]

That means "this is dirty"