The English language has a plethora of words which look and sound very similar and are easy to confuse and misuse. Here, a professional proofreader, editor and writer demystifies some commonly confused words.

The English language has a plethora of words which look and sound very similar and are easy to confuse and misuse. In my work as a proofreader and copy editor, I come across plenty of confusion over these words. Below are some of the main ones to watch out for in your writing.

Affect or effect? Affect means to make a difference to . . . I am not affected by what you are saying. Effect means to bring about a result . . . The effects of the storm were widespread.

For ever or forever? For ever means 'for always' . . . I will be your friend for ever. Forever means 'continually' . . . He was forever missing the bus.

It's or its? It's is the contracted form of 'it is' . . . It's a sunny day today. Its means 'belonging to it' . . . The dog ate its dinner.

Know or no? To know means to understand . . . I know how to cook. No is the opposite of yes . . . No, I don't want to go out.

Licence or license? Licence is the noun . . . I have a driving licence. License is the verb . . . Are you licensed to serve alcohol?

Of or off? Of indicates possession or association . . . The coat of my brother. Off is the opposite of on . . . Did I turn the oven off?

Principle or principal? Principle is a noun meaning 'basic truth or guideline' . . . Vegetarians avoid meat on principle. Principal can be an adjective or a noun meaning 'first in rank or importance' . . . She is the principal dancer in the ballet.

Their or there or they're? Their means 'belonging to them' . . . The girls played with their toys. There is the opposite of here . . . The book is over there. They're is short for 'they are' . . . They're going to the seaside.

To or two or too? To is a preposition . . . We're going to the zoo. Two is a number . . . The animals went in two by two. Too means 'also' . . . I like chocolate too.

Whether or weather? Whether sets out alternatives . . . I don't know whether to walk or catch the bus. Weather means the climate . . . Scotland has wet weather.

Where or wear or were? Where attaches to a location . . . Where is London? Wear is a verb meaning 'to be dressed in' . . . What are you wearing to the party? Were is the past tense of the verb 'to be' . . . Were you at work yesterday?

Your or you're? Your means 'belonging to you' . . . Where is your coat? You're is short for 'you are' . . . I think you're right.