Meaning: If you calm down, you stop being angry or excited and become more relaxed.
Grammar: This phrasal verb can be used with or without an object. The verb can be separated from its particle. If the object is a pronoun, it must go between the verb and the particle.
He's calmed down
Can you calm the children down?
Can you calm them down?
She calmed down the children (this is rare)
She calmed down them
Example sentence: Since you left last month, the situation is getting better and things have calmed down.
Synonyms: relax, quieten down, settle down, ease off, take it easy, subdue