だけ

particle

in a negative, limiting sense: only, just, limit / in a positive, non-limiting sense: amount, as much as

He can not only speak Japanese, but also write it.

意味（1）

in a negative, limiting sense: only, just, limit

ローマ字(じ)だけの辞(じ)書(しょ)

Rōmaji dake no jishorōmaji-only dictionary

意味（2）

in a positive, non-limiting sense: amount, as much as

寝(ね)たいだけ寝(ね)ていい。

Netai dake nete ii.You can sleep as much as you want.