Wiktionary
n. A stage in human development, generally including toddlerhood and some time afterwards.
WordNet
Wikipedia
Early childhood is a stage in human development. It generally includes toddlerhood and some time afterwards. Play age is an unspecific designation approximately within the scope of early childhood. Some age-related development periods and examples of defined intervals are: newborn (ages 0–5 weeks); infant (ages 5 weeks – 1 year); toddler (ages 1–3 years); preschooler (ages 3–5 years); school-aged child (ages 5–12 years); adolescent (ages 13–19).
Usage examples of "early childhood".
Jimmy thought back over his early childhood, before the education fizzle, and it was true that he and the other boys had been the egocentric little animals Bard described.
He could just remember, in his early childhood, someone explaining that light existed by itself, but shadows only when something stood before the light.
Some people say they can recall such experiences from early childhood.
On this body of data the door was locked in early childhood by the firm directives, 'Don't ask questions.
Like the autobiography of Hugh Miller, it carries us so far back into early childhood, as to throw light upon the question, “.
I just got lonesome and acted on it with somebody I've known since early childhood.