1.
it can't be helped; there's no choice; it's inevitable
Expresses resignation or acceptance that nothing can be done about a situation. A very common Japanese expression reflecting acceptance of circumstances.
こうなってしまったらしかたがない。
Since it's come to this, there's nothing we can do.
2.
can't help doing; can't stop oneself from
When preceded by a verb in て-form, expresses that one cannot help doing something.
Forms
仕方 (way, method) + が + ない (doesn't exist)
Literally: "there is no way/method"
Common patterns
- 〜てしかたがない = can't help but ~, unbearably ~
Example: 寂しくてしかたがない (unbearably lonely)
- 〜でしかたがない (same meaning, after na-adjectives)
Cultural note
This is one of the most important expressions in Japanese culture, reflecting the concept of accepting what cannot be changed. It's not defeatism but rather a form of practical acceptance.
Register
Neutral. Appropriate in most situations.