The word "youngster" typically refers to a child or young person. However, there are many synonyms that can be used to describe individuals who are still in the early stages of their lives. Some options include "juvenile," "adolescent," "teenager," "youth," "minor," "child," "kid," "toddler," and "infant." Each of these words is a suitable replacement for "youngster," depending on the age range being described. It's important to choose the right synonym based on the context and tone of the writing or conversation. For example, the word "juvenile" is often used in a more formal or legal context, while "kid" is a more casual or playful term.