1. contain or hold back emotions. Very common subdue, hold back, or contain emotions different speakers prefer one or other of these three word. 2. Hold back, contain a/the fire. Very common. some speakers would use any one of the four options. 3. subdue, contain the melee . very common A) subdue to overcome or contain keep within bounds, a fire would need to be contained with the space it started without spreading elsewhere. is the basis of "fire control" B) contain = to control by containment. keep within bounds. C) restrain = prevent someone doing something. Or to keep something within limit stop it getting out of control. D) hold back = to prevent "oneself" from doing something to refrain from punching you nosey neighbour/neighbour on the nose. to hesitate. Although many speakers do use it in the situations you describe. To express stopping it at a predetermined point. fire breaks in forests and dams and dykes/ditches in flood plains do this. I would say "contain the fire, to suppress it until it is extinguished" "subdue and contain a melee" overcome it and keep it under control. Police boxing in protesters use this tactic. "subdue/suppress and hold back/contain emotions" don't let them explode. "Restrain a single person or group of people" by physically disabling them, throw them in the back of a police van in handcuffs, lock them in a cell. Restrain is more commonly used for people and there is a little overlap and interchangeability for other things, with the other three words. It depends on what you more precisely wish to express. And your preference.

Very little differences For emotions all would be interchangeable For fire or flood you wouldn't restrain it as restrain is more a personal physical action and while a fire could be subdued a flood couldn't and would generally subside . Very subtle differences mostly due to physical characteristics.

what does the dictionary say?

Almost no differences in case of emotions and fire.