This post is about a really common grammar error found frequently in informal writing on internet forums or in Twitter and Facebook posts. How many times have you come across sentences like this: ‘I would of called you but I was busy’, ‘I could of done that’, ‘I should of met him there’? I’m guessing pretty often – I know it’s a mistake I pick up all the time.
I think it’s an error that’s found more often among native speakers than learners of English. In the huge amount of non-native English that I’ve proofread since setting up my business, I’ve yet to come across this mistake in academic English.
Why does this mistake happen?
The main point of confusion comes from the fact that when unstressed, have and of sound alike. In fast speech, especially when people are chatting informally, both forms are frequently unstressed.
So instead of writing ‘could/should/would have’, or the contracted forms ‘could’ve/should’ve/would’ve’, some people confuse the two sounds in their written English and write ‘could/should/would of‘.
Key points to remember
Let’s take the following sentence as an example (I’ve used ‘could’, but what I say applies equally to ‘should’ or ‘would’):
a) *You could of called me
b) You could have called me
c) You could’ve called me
To avoid producing incorrect sentences like (a) instead of (b) and (c), it helps to understand ‘of’ as a part of speech. It’s a preposition, which is defined in collinsdictionary.com as:
a word or group of words used before a noun or pronoun to relate it grammatically or semantically to some other constituent of a sentence.
You can see in the example sentence (a) that ‘of’ doesn’t occur before a noun or pronoun, but before ‘called’, which is a verb. In this context, a preposition is not grammatically acceptable.
In contrast, it’s perfectly acceptable for ‘could have’ (or the contracted form ‘could’ve’) to appear in this position in the sentence. ‘Could’, ‘would’ and ‘should’ are all modal auxiliary verbs, meaning that they occur before a main verb to add information such as possibility, intention, permission and likelihood.