Answer:
The word amateur comes from the Latin "amat" meaning he (or she !) loves. An amateur is a person who does something for the love of it, not because he has to or makes money at it. He is usually knowledgeable, often beyond the level of many professionals; every amateur was a beginner once, but it doesn't last long!
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Since this question is in amateur radio, the answer should be specific to the "amateur" in "amateur radio." In this case, it means that the amateur radio operator cannot use radio for pay or profit.
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Amateur radio operators have invented almost every type of electronic communication protocol that has ever been used. They are very good at what they do! Some people confuse amateur radio operators with citizen's band (CB) operators... CB operators are not required to be licensed nor know anything about radio communication... where-as, amateur radio operators must pass a Federal Government written test about electronics, radio control and operation, along with the rules and regulations set forth by the FCC. Amateur radio operators are the 'professionals' in non-paid electronic communications, electronic and satellite development and emergency communication.