Are you a stickler for good grammar? Perhaps you’d even go as far as to call yourself a grammar geek? Well, whether you’re the sort of person who prides themselves on their flawless grammar, or a hapless essay writer looking for a trick or two, this post will introduce you to some of the more unusual grammar rules you should know.

Below are six common grammatical mistakes we see routinely, not just in undergraduate essays, but also in professional publications like newspapers, magazines and even best selling novels. With that said, here are some weird grammar rules you might not know.

Which and That

This is a common mistake that even professional writers regularly make. You might think these two can be used interchangeably, but you’d be wrong.

‘That’ is a restrictive pronoun, so it’s vital to the noun to which it’s referring, e.g. I don’t trust second hand cars that aren’t nearly new. So in this instance, I trust all second hand cars that are nearly new.

‘Which’ introduces a relative clause that allows non-essential qualifiers, e.g. ‘I only trust second hand cars that are nearly new, which come from the Ford or Renault garage.’ So while ‘that’ restricts, ‘which’ is used to add more detail.

May and Might

Again, most people assume these two words can be used interchangeably, but there is a subtle difference in their meaning.

‘May’ implies a possibility, whereas ‘might’ implies far more uncertainty. For example: ‘I may fall over if I drink all that wine’ implies a good chance of falling over, but ‘I might start singing once the karaoke begins’ implies it’s not that likely to happen.

Fewer and Less

This is an excellent example of one of the grammar rules in essay writing which is commonly broken. Thankfully it’s actually a very simple one to remember.

‘Less’ is reserved for hypothetical quantities, whilst ‘few’ and ‘fewer’ are reserved for items you can actually quantify. For example, ‘the firm is less fun to work for now we have fewer than five employees’.

Affect and Effect

This one is not so much an example of a weird grammar rule, but one you absolutely must know. Both of these words are extremely common, but it’s amazing how many people get them wrong. However, it’s actually very easy to differentiate between the two.

‘Effect’ is almost always a noun, and ‘affect’ is almost always a verb. So ‘the effects of alcohol can be damaging’ describes the result or outcome of drinking alcohol. Affect is used to describe the influence or cause of an impression i.e. ‘alcohol’s affects can be damaging’.


This doesn’t fit into the bracket of weird grammar rules. Instead, it’s just a word that’s not a word, born and bred in the corporate jungle. Please don’t use it, no matter how ‘impactful’ you want to be.

Comma Use with Adjectives

– Use commas to separate coordinate adjectives as in the following: ‘The unkempt, brilliant man was always unhappy.’

– Do not use commas to separate cumulative adjectives: ‘The long yellow car circled the factory.’

– Do not use a comma when the adjective modifies both the noun and the other adjectives modifying it: ‘The late humorous and generous Mr Welby will be sorely missed.’

– Comma use with descriptive adjectives can also be determined by the class of adjective, i.e. age, size, colour, shape, material, origin and general. If multiple adjectives from the same class appear, separate them with a comma: ‘The sad, broken man fell into the smelly, murky lake.’

Tripping over grammar?
We pride ourselves on the use of well known and lesser known points of grammar. So, if you’re worried about the weird grammar rules in essay writing, we’ll be happy to help you out by giving your essay a thorough going over, so you can be assured that it says exactly what you intended it to.