What it means
しか～ない marks a strict limit. It means that the stated noun, amount, or action is the only one that applies, with the negative form making the meaning "only" or "nothing but." With a noun, it often means that there is only that thing. With a dictionary-form verb, ～しかない often means that there is no choice but to do that action. This pattern is stronger than simply saying だけ.
Usage note
しか must be used with a negative ending, such as ない or ありません. Do not use it with a positive ending. Unlike だけ, しか～ない emphasizes that nothing else is possible or included.
How to use it
冷蔵庫には水しかありません。
There is only water in the refrigerator.
週末は家で休むしかありません。
There is no choice but to rest at home on the weekend.
冷蔵庫には水しかない。
There is only water in the refrigerator.
週末は家で休むしかない。
There is no choice but to rest at home on the weekend.
Example sentences
冷蔵庫には卵が二つしかありません。
There are only two eggs in the refrigerator.
今週は図書館へ行く時間が一時間しかありません。
This week, I have only one hour to go to the library.
この箱にはりんごが三つしか入っていません。
There are only three apples in this box.
旅行の準備に必要