The time when you are a child is yourchildhood.
My childhood was spent moving from place to place as my father was in the army.
You can also useboyhoodfor the childhood of a boy, orgirlhoodfor the childhood of a girl.Girlhoodis old-fashioned and is not as common asboyhood.
He remembered his boyhood as an idyllic period of his life.
Not since her girlhood had she felt so free and uninhibited.
The time when someone is an infant is theirinfancy.Infancyis often used in more formal or technical contexts.
Many more children used to die in infancy.
Someone'syouthis the time when they are young.
At 25, he felt his youth was already coming to an end.