someone who is not familiar with or has no experience in a particular field; a non-professional

In astronomy, any planet in our solar system whose orbit is further from the sun than the earth's orbit.

speech or opinions expressed by someone who lacks professional knowledge or experience in a particular field

experts look for the deeper meaning and technique in a performance or task while laymen only look at the surface-level spectacle

actions that violate established rules, regulations, or social norms