Mono is a term that can refer to several things, but one common meaning is a type of viral infection known as mononucleosis. Often called "mono," this illness is typically caused by the Epstein-Barr virus and is most commonly seen in teenagers and young adults. Symptoms include extreme fatigue, sore throat, fever, and swollen lymph nodes. Another meaning of mono is related to audio technology, where it refers to monophonic sound. Unlike stereo sound, which uses two channels to create a sense of space and depth, mono sound uses a single channel. This means that all audio is mixed together and played through one speaker, making it simpler but less immersive.