A point-contact transistor, also known as a junction transistor or a bipolar transistor, is an electronic device commonly used in circuits. These transistors come in various shapes, sizes, and types, depending on their specifications. Other synonyms for point-contact transistor include germanium transistor, NPN transistor, PNP transistor, and field-effect transistor. Germanium transistors utilize germanium as their semiconductor material, while NPN and PNP transistors allow current to flow through their base, emitter, and collector regions in different ways. Field-effect transistors use a different principle, where the current is controlled by the strength of an electric field. All of these synonyms can be used interchangeably, depending on the context and application.