Rookie (noun)

1. A new recruit or beginner in a particular field or organization.
2. A first-year player in a professional sport.

Origin:

1930s: of unknown origin.

Examples:

1. He's a rookie on the police force.
2. She's a rookie in the stock market.
3. He's a rookie in the NFL.
4. The rookie made a mistake.
5. She's the rookie of the team.