mischief
n. uncountablen. playful behavior that causes trouble or annoyance but is not meant to be serious or harmful. You often use it to describe children or pets being naughty.
n. playful misbehaviour or trouble-making that results in minor harm or annoyance. Often carries a lighthearted or affectionate tone when applied to children or animals.
The children are always getting into mischief when they are bored.
The puppy caused a bit of mischief by hiding everyone's shoes under the sofa while they were sleeping.
While his actions were technically a breach of the rules, the headmaster recognized them as harmless mischief rather than a calculated attempt to undermine school authority.
From Middle English myschef, meschef, meschief, mischef, from Old French meschief, from meschever (“to bring to grief”), from mes- (“badly”) + chever (“happen; come to a head”), from Vulgar Latin *capare, from Latin caput (“head”).
From Middle English myschefen, myscheven, from Old French meschever.
Commonly appears in the phrase 'get into mischief' or 'up to mischief'.
He did many mischiefsHe did a lot of mischiefMischief is uncountable; use 'acts of mischief' or 'a lot of' if you want to describe multiple instances.