Common Mistakes in Writing

See also: Formal or Informal Writing Style

Some writing mistakes are very common and frequently seen in both printed material and online. This page details some of the most common and easily avoidable writing mistakes. By learning to recognise such errors you can improve your writing skills and avoid common writing mistakes in the future.

You should also read our Spelling, Punctuation and Grammar pages to aid your understanding of the writing process and help you avoid other mistakes.

Remember mistakes in writing can be embarrassing and costly - would you buy from a company whose marketing material was peppered with common mistakes that could have been easily avoided?

Take some time to familiarise yourself with the mistakes listed on this page and remember to always get somebody else to check your writing before it is published - even the most confident writers make mistakes sumtimes!

Affect / Effect

  • Affect is a verb, for example “Sometimes, the weather affects my mood.
  • Effect is a noun, for example “The effect of weather on ice cream sales is well documented.

By thinking in terms of “the effect” you can usually determine whether to use affect or effect since “the” will not work in front of a verb.   

To add to the confusion, bear in mind that some people may use “effect” as a verb (for example “Contractors seek to effect a settlement with strikers”) but this usage is slightly archaic and most often used in legal writing.


Apostrophes strike fear into the heart of many. However by learning a few simple rules, and the inevitable exceptions, you should be able to use apostrophes with ease.

The apostrophe is used for a purpose, either to indicate a possession (implying ownership) or a contraction (in place of other letters). Since its use to indicate a contraction is easiest, we will deal with this first.

Using Apostrophes to Indicate Contraction

Where one or more letters have been dropped, an apostrophe is used as a replacement:

  • It is = it’s
  • We are = we’re
  • Does not = Doesn’t
  • Of the clock = o’clock

Using Apostrophes to Indicate Possession

Apostrophes are also used to indicate possession:

  • Matthew’s car
  • The farmer’s field (one field owned by one farmer)

If the subject (the farmer or Matthew above) has a name ending with an s, then there is a choice to either follow the formal rule (“The Jones’s house”) or to drop the final 's' (hence “The Jones’ house”).  The choice is a matter of style but the important thing is to be consistent.

If the subject is plural, the apostrophe is placed after the s:

  • The teachers’ staff room
  • The farmers’ fields (multiple fields owned by multiple farmers)

Note that if the word is already plural, for example children or people, then you would write children’s or people's.

When Not to Use Apostrophes

If the word is a plural then do not use an apostrophe (for example kittens or apostrophes).  Placing an apostrophe before the final s is universally considered incorrect and commonly referred to as the “greengrocer’s apostrophe” (or “greengrocers’ apostrophe” if referring to more than one greengrocer).

There are possible exceptions to these rule is if the word comprises a single letter, a number or abbreviation where the simple addition of an s could cause confusion. Hence:

There are two t’s in Matthew.

To write “There are two ts in Matthew” may confuse the reader even though it is grammatically correct.  Alternatively, you could rephrase this as “There are two “t”s in Matthew”.

However, the modern convention is to avoid using apostrophes in plurals wherever possible even in the plural of numbers and abbreviations.

For example, “I keep buying DVDs” and “He loves 80s music” is preferable to adding an apostrophe.

Could have / Should have / Would have

Even though we might pronounce “could’ve” (a contraction of “could have”) as “could of” this is incorrect.  Always use could have / should have / would have.

It’s / Its

  • It’s is a contraction of two words: it is or it has.
  • Its is possessive, like hers, his, and whose.

The confusion between it's and its occurs because on virtually every other word 's (apostrophe + s) indicates possession, so English speakers naturally want to use it's to mean "something belonging to it."

But 'it's' is only used when it is a contraction of 'it is' or 'it has'.

If you are in doubt as to which version to use, try replacing the word with "it is" or "it has". If this still scans correctly then use it’s, otherwise, use its.

There / Their / They’re

  • There refers to a place or idea. An example of its use referring to place is “Look over there!”  An example of its use referring to an abstract idea is “There are many ways to skin a cat”.
  • Their is possessive meaning it owns something, for example “Their dog keeps getting into our garden”.
  • They’re is a contraction of “they are” (the apostrophe replaces the missing letter). An example of its use is “They’re moving in next door”.

There’s / Theirs

  • There’s is a contraction of there is.
  • Theirs is the third person plural possessive pronoun and replaces “their + noun”. The idea that theirs needs an apostrophe (hence “their’s”) derives from the convention that, in virtually every other word, ‘s (apostrophe + s) indicates possession. However, theirs is an exception and “their’s” is incorrect.

To / Too / Two

'To' has two functions. First, it is a preposition and always preceded a noun, hence:

  • I am going to the shops
  • This belongs to Mary

Second, 'to' indicates an infinitive when it preceded a verb, hence

  • I need to sleep
  • He wants to go for a walk

'Too' also has two uses, the first as a synonym for “also” hence:

  • Can I come too?
  • I think that’s his bag too

Second, 'too' means excessively when it preceded an adjective or adverb hence:

  • I’m too tired to go out
  • You’re too generous

'Two' is a number as in one, two, three…

The most common confusion is between to and too.  Try replacing the word with “also” or “as well” and if the phrase makes sense then use too. Otherwise, and if not a number, then use to.

Frequently Misused Words


Strictly, decimate means to reduce by one-tenth and not to reduce to one-tenth.  However, this usage is now increasingly common, and seems likely to become accepted.

Literally, practically, figuratively and metaphorically

Literally means actually or without exaggeration. When you say “I literally…” you are describing something exactly as it happened and without exaggeration. If you were to say “I literally died of boredom”, you are implying that you actually died. The use of literally is therefore incorrect.

Instead, you might use the term ‘practically’, which in this case would mean ‘almost’. “I practically died of boredom” means “If it were actually possible to die of boredom, I would have done so, but as it’s not, I didn’t.”

The opposite of literally is figuratively or, more specifically, metaphorically.

  • Figuratively means that you are using a figure of speech, such as a metaphor or a simile.
  • Metaphorically means that you are using a metaphor, which is a specific figure of speech.

In other words, most of the time when people say literally or practically, they actually mean figuratively or metaphorically.

Lose / Loose

Lose is the opposite of win, whilst loose is the opposite of tight or contained.

Weather / Whether

Weather is usually a noun referring to the atmospheric conditions at a particular point in time (What’s the weather like there?) but is also a verb meaning' affected by the weather (for example: "Your fence has really weathered") or even as a figure of speech meaning to get through or survive something (We weathered the crisis).

Whether is a conjunction that introduces alternatives, for example “Whether I win or lose…” or “You do it whether you like it or not”.  Whether is similar to “if”, so if you could replace the word with “if” then use whether.


This page is a very brief introduction to some of the most common mistakes found in English writing.

However, you can see that the English language is unfortunately complex and most spelling and grammar checkers will not pick up subtle distinctions between some of the often-confused words above. Likewise, such checkers will not pick up mistyped words such as “fir” instead of “for”, or “if” instead of “it” or indeed spot all missing words.

It is vital that you therefore do not rely on a spell checker to proofread your writing for you.

The best advice is to read your writing or, better still, to get someone else to read it and check it for you. Most people find it easier to spot errors when reading from a printed copy compared to reading on a computer screen, so print out a copy to read.