只
zhī
Expressing "only" with "zhi"
只 is the neutral "only", and like every adverb it goes before the verb.
只 + Verb
How it works
我只有一个妹妹 — I only have one younger sister. No judgement attached, unlike 才.
只 always sits in front of the verb, even when English would put "only" next to the noun. 我只买了一本书, not 我买了只一本书.
只有 also opens the "only if" conditional, which is a separate pattern.
Examples
wǒ zhǐ yǒu yí gè mèi mei
我只有一个妹妹。
I only have one younger sister.
wǒ zhī mǎi le yì běn shū
我只买了一本书。
I only bought one book.
tā zhī hē chá, bù hē kā fēi
他只喝茶，不喝咖啡。
He only drinks tea, not coffee.