A youngster is a young person, typically a child or adolescent, who is relatively inexperienced in the ways of the world.
The term often implies a sense of youthfulness, naivety, and potential. It can be used affectionately or slightly patronizingly, depending on the context and tone. While 'youngster' generally refers to humans, it can occasionally be used in a figurative way to describe something new or immature, such as a young business or a fledgling idea.
TOT LAD TAD KID FRY BOY CUB PUP
TYKE TIKE
CHILD MINOR YOUTH
NIPPER SHAVER MOPPET
TIDDLER
NESTLING SMALLFRY TEENAGER JUVENILE
STRIPLING
SPRINGCHICKEN