This is the 235th most frequent German word.
nur
Only.
Here, 'nur' limits the quantity, indicating that the action of eating was restricted to one apple.
Ich habe nur einen Apfel gegessen.
I only ate one apple.
In this case, 'nur' expresses intent, suggesting that the person's motive was simple or limited to helping.
Er wollte nur helfen.
He just wanted to help.
Here, 'nur' denotes a wish or longing, adding emphasis to the speaker's desire for a situation.