"NPN" is a commonly used abbreviation for "N-type semiconductor, P-type semiconductor, and N-type semiconductor" which refers to a specific type of transistor. However, there are various synonyms for the term "NPN" which are frequently used in the field of electronics. Some of the most commonly used synonyms for "NPN" include Bipolar Transistor, NPN Transistor, and Semiconductor Transistor. Other synonyms for NPN may include Negative-Positive-Negative transistor, P-N-P transistor, and N-type bipolar junction transistor. Regardless of the term used, all these synonyms describe the same type of transistor, which is commonly used in electronics to switch and amplify electrical signals.