Synonyms: Immature

Adolescens is Latin for "a young person."

Amateur is French, from the Latin verb amare, meaning "to love." An amateur is one who does an activity — a sport, a hobby, a creative pursuit — for the love of it, not necessarily due to exceptional skill. The essential meaning is the opposite of professional, and it can be a complement or an insult depending on the context and the quality of the result.

A Germanic word, callow originally meant "bald" or "hairless." Because it referred to baby birds, among other things, the associated meaning of "young, new to the world, and inexperienced" is the one that stuck.

Credulous is a synonym for gullible: describing someone who will believe nearly anything.

Guile is deceit, or sneaky dishonesty, so someone without that is innocent and therefore vulnerable to deception.

A French word, from the Latin ingenuus, ingenue is often seen in dramatic contexts, describing a particular character type: a vulnerable young woman.

From the same root as ingenue, above, ingenuous is another synonym for "naive" or "inexperienced."

Jejunus means "fasting" in Latin, so jejune can mean "thin," "lacking," or "empty." Its additional sense of "immature" may be due to the mistaken notion that it relates to the French jeune, meaning "young."

Another French word, meaning "immature," "innocent," or "guileless," naive is actually the feminine form of the word. A male would be called naïf.

A sophomore is a second-year high school or college student, but a sophomoric argument is illogical, ill-informed, or specious.