Companion
- A full-time missionary's assigned partner. Missionaries are never supposed to be alone, so each one is paired with a companion and the two are expected to stay within sight and earshot of each other 24 hours a day.
Companion assignments are made by mission leadership and change every several weeks through a process called a "transfer." A senior companion has usually been in the field longer and takes the lead, while the junior companion is newer. Being stuck with a companion you don't click with is sometimes jokingly compared to a marriage — hence the affectionate/exasperated slang "comp."