Translation guide
Describes something that is extremely easy or trivial to do, often with a dismissive or playful tone. In Japanese, this is expressed through set phrases, adjectives, and figurative expressions rather than a single direct translation.
To say that something is very easy, like a task that even a child could do.
Literally 'before breakfast,' meaning something is so easy you can do it before eating. Very common and natural.
This kind of work is child's play.
A playful, somewhat old-fashioned phrase meaning 'a piece of cake' or 'child's play.' Often used in casual speech.
That's child's play!
Literally 'like twisting a baby's hand,' meaning extremely easy. Somewhat dramatic and less common in daily conversation.
Defeating him is child's play.
To dismiss something as not serious or not worth worrying about.
Both mean 'very easy,' but 朝飯前 is more standard and widely used. お茶の子さいさい has a playful, slightly old-fashioned ring and is more common in casual, friendly contexts.
Do not translate 'child's play' literally as 子供の遊び (kodomo no asobi). While understandable, it sounds unnatural and is not idiomatic. Use the phrases above instead.
For a pro like you, this is child's play.
Don't worry, the test was child's play.
His argument is child's play.