turn on

You can use it in two ways. You can say turn on the light or turn the light on. Both are perfectly correct. If you use a pronoun like it, you must put it in the middle: turn it on. Don't say turn on it or your friends might look a bit confused! It's a very flexible phrase for anything with a power cord or a battery.

Use it the moment you walk into a dark room. Use it when you want to watch a movie with friends. It’s great for the office when you need to start your laptop. You’ll also use it in a car for the heater or the radio. Basically, if it has a plug or a power button, this is your go-to phrase.

Don't use turn on for things like fire or candles. For those, we say light. Also, avoid using it for people in a professional setting. In a romantic context, turn on has a very different, adult meaning. Stick to machines and electronics at work to avoid a very awkward HR meeting! Also, don't use it for opening a door or a book.

This phrase comes from the old days of machinery. You literally had to 'turn' a physical knob or handle to connect the electrical circuit. Even though we mostly just tap glass screens now, the word turn stayed with us. It’s a linguistic ghost of old technology. In the 1960s, it also became a slang term for excitement, but keep that for casual Friday nights.

You might hear switch on which is exactly the same thing. In some places, people say power up for computers to sound a bit more high-tech. If you are feeling very lazy, you might just say hit the lights. But turn on is the king of them all. It’s understood everywhere from London to New York to Sydney.