hanamaru
Say there is only (not enough)
しか〜ない means 'only', with a hint that it isn't as much as you'd like.
JLPTN5
... しか ... ない~ shika ~ nai
only ~ (and that's not enough)
Use しか together with a negative verb to mean 'only', with the feeling that it is less than you'd want. The verb must be negative even though the meaning is positive in English. Compare it with だけ, which says 'only' neutrally without the sense of shortage.
Tips and Common Traps
Hana· Key point
Use しか〜ない when you want to sound a little disappointed — like 'I only have five minutes' or 'there's only one left'. The sense of 'not quite enough' comes built in.
Maru· Common trap
The verb must be negative even though English says it positively: 一つしかない (there is only one) — never 一つしかある.