Megacycle per second (Mc/s) is a unit of frequency used to measure the number of cycles per second in electronic communication systems. There are several synonyms for this term, including megahertz (MHz), which is the more commonly used term in modern times, and kilomegacycle per second (KMc/s). Another synonym is million cycles per second (Mcps), which is a common term used in telecommunications. Additionally, the term gigacycle per second (Gc/s) is also used to describe frequency on a larger scale. Overall, these various synonyms can be used interchangeably depending on the context and the specifics of the technology involved.