Pyjama and Trouser

Pyjama noun - A pair of loose trousers tied by a drawstring around the waist; worn by men and women in some Asian countries.

Trouser and pyjama are semantically related. In some cases you can use "Trouser" instead a noun "Pyjama".

Trouser noun - (usually in the plural) a garment extending from the waist to the knee or ankle, covering each leg separately.

Pyjama and trouser are semantically related. Sometimes you can replace term "Pyjama" with "Trouser", this nouns are similar.