Infantile (adjective)

1. Relating to or characteristic of an infant or early childhood.
2. Immature or juvenile in behavior.

Origin:

From latin infans (unable to speak) + -ile (pertaining to).

Examples:

1. The infantile scribbles on the wall were a reminder of the child's presence.
2. His infantile behavior was not appropriate for a grown man.
3. The infantile stage of human development is crucial for physical and cognitive growth.
4. He had an infantile need to be the center of attention.
5. Her infantile innocence was endearing, she still believed in Santa Claus.