The English language is complex, and it’s difficult for even native speakers to know all of the intricacies of its grammar rules. Here are a few of the more difficult grammar rules you can teach your students to help them master the purist’s version of the English language.

1. Who v whom

Whom should be used to refer to the object of a verb or preposition. For example, in the sentence “To whom was the letter addressed?”, the object is having a letter addressed to them. When in doubt, try this simple trick: If you can replace the word with “he”’ or “’she,” use who. If you can replace it with “him” or “her,” use whom. Another good way to determine when to use whom is if there’s a preposition in front of it, like ‘by’, ‘with’ or ‘on’.

2. Sentences ending with a preposition

A preposition is a word that indicates the relationship between two nouns (things), like ‘on’, ‘with’ and ‘in’. Sentences should not end with prepositions. For example, ‘There is nothing to be afraid of’ is technically wrong, though it sounds natural.

3. Starting a sentence with a conjunction

Technically, you’re not supposed to start a sentence with a conjunction like ‘and’ or ‘but’. However, it’s becoming more and more common. You can probably get away with it in a blog article, a novel or a poem, but should avoid starting sentences with conjunctions in academic writing.

4. Different to v different from

Many people say ‘different to’, however the correct term is actually ‘different from’, just as you would use ‘from’ after the word ‘differ’. For example, you would say ‘apples differ from oranges’. You wouldn’t say ‘apples differ to oranges’.

5. One word sentences

Conventionally, a complete sentence requires a subject and a verb. However, sometimes in one word sentences, the subject and the verb are implied, meaning the one word sentence is understood in the context of the sentences around it so that the subject and/or verb doesn’t have to be explicitly stated. For example, ‘Go!’ rather than ‘Get going now!’, or ‘Help!’ rather than ‘I need your help!’.

6. Split infinitives

An infinitive is a construction such as ‘to go’ and ‘to be’. Purists believe infinities shouldn’t be separated by placing a word in between. For example, the famous Star Trek quote, ‘to boldly go’, is in fact, incorrect.

7. Who v that

This is one of the most common grammatical errors in the English language. ‘Who’ should be used when you’re talking about a person, and ‘that’ is used when referring to an object. For example, ‘I spoke to a woman that said…’, should be ‘I spoke to a woman who said…’.

8. Referring to a company as singular

Companies are often referred to as plural because it considers the fact that a company is made of a group of people. For example, ‘XYZ are a great company’. However, a company is a single entity and should be talked about like this: ‘XYZ is a great company’.

9. Try and v try to

The correct phrase is ‘try to’, as trying is part of the action. You don’t ‘try and learn to the play piano’; rather, you ‘try to learn to play piano’.

10. E.g. v i.e.

E.g. and i.e. are often used interchangeably, however they have different meanings. E.g. stands for ‘exempli gratia’, a Latin phrase meaning ‘for example’. It should be followed by any number of examples from a set of possible examples. Contrastingly, i.e. stands for the Latin phrase ‘id est’, which means ‘that is’. Therefore, i.e. should be followed by all of the applicable examples.

11. Compound possession

Compound possession is when you’re talking about possession and there are two subjects. You must determine whether the two people possess the object together, or separately. For example, in the phrase ‘Peter’s and Karen’s cars are blue’, Peter and Karen do not share ownership of their blue cars, rather, they each own one or more blue cars. On the other hand, ‘Peter and Karen’s cars are blue’, means Peter and Karen share ownership of at least two blue cars.

12. Couldn’t care less

Many people mistake this phrase by saying ‘I could care less’. This is incorrect as ‘could care less’ means that you do still have some level of care about the subject to give. The phrase is used to mean that you have no care at all about the subject, so it should be ‘I couldn’t care less’.

13. Parentheses at the end of a sentence

Parentheses, or brackets, allow a writer to provide additional information. If the parenthetical phrase is at the end of a sentence, the terminal punctuation mark must be placed outside of the parentheses. For example, ‘The children wanted to go to the park (they love kicking the soccer ball).’ is the correct way to write this sentence. However, if the parenthetical is a full sentence and not part of another sentence, the punctuation mark is included within the parentheses like this, ‘It was true. (But even if it wasn’t, who would know.)’.