I'm reading a book Key Words For Fluency and I found there a topic about heating. There are two sentences:

Turn the heating on/off.

Set the heating to come on at 5 and go off at 9.

Could you explain to me the difference between these phrasal verbs (turn on/off and come on/goes off) in such context?


In the context of machines or systems such as heating systems, computers, etc, the difference is that a person turns a machine on or off, but a machine can come on or go off by itself (e.g. if it has a time switch). Electricity in a house can go off if there is a power failure and come (back) on again later.

To turn something on in this context means to make it work by pressing a switch, pulling a lever, etc.

Definition of turn on
transitive verb
1: to activate or cause to flow, operate, or function by or as if by turning a control
turn the water on full
turn on the power

Turn on (Merriam Webster)

In this context also, if something

comes on, it starts working

Come on
phrasal verb
to start to happen or work
The heating comes on at six in the morning

Come on (Cambridge Dictionary)

  • So the difference is in the way it starts working. Turn on - by a human; Come on - by itself. Thank you.
    – BBQBoi
    Mar 7 '21 at 22:59
  • @BBQBoi That's correct. You will sometimes hear "Turn itself on" instead of "Come on". That is a valid expression too.
    – BoldBen
    Mar 8 '21 at 6:22

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