Number + 只 + Animal Noun
The classifier 只 (zhī) is used when counting small animals such as dogs, cats, birds, and insects. It is placed between a number or demonstrative and the animal noun, as in 一只小狗 (a small dog) or 两只猫 (two cats).
他养了一只小狗和两只猫。
Tā yǎng le yī zhī xiǎo gǒu hé liǎng zhī māo.
He has a puppy and two cats.
树上有一只小鸟在唱歌。
Shù shàng yǒu yī zhī xiǎo niǎo zài chànggē.
There is a little bird singing in the tree.
我在路上看见了一只很大的蜘蛛。
Wǒ zài lù shàng kànjiàn le yī zhī hěn dà de zhīzhū.
I saw a very large spider on the road.