the time of person's life when they are a child
"Her childhood was filled with summers spent exploring the woods behind her house."
The state of being a child.
"The nostalgia for her childhood brought back vivid memories of playing in the park every afternoon."
In plain English: Childhood is the time when you are young and not yet an adult.
"He cherished his childhood memories of playing in the park with his friends."
Usage: Use childhood to refer to the entire period of time from birth until adulthood, rather than describing a specific moment when someone is young. It functions as an abstract noun representing that developmental stage in general.
Childhood comes from the Middle English word childhode, which was borrowed directly from Old English ċildhād. The term originally referred to the state of being a child, combining the root for "child" with the suffix meaning "-hood."