IPA: /ˈkɪndərˌɡɑːrtənər/
KK: /ˈkɪndərˌɡɑrtənər/
A child who is in the first year of school, usually around five years old, where they learn basic skills and socialize with other children.
My son is a kindergartener and loves to play with his friends at school.
Kindergartener → It is formed from "kinder" (from German "Kind", meaning child) and "garten" (meaning garden). The word refers to a person who is in a garden of children, specifically a teacher or student in a preschool setting.
Think of a 'garden' ('garten') where 'children' ('kinder') play and learn together — that's what a kindergartener is.