Having the ability to express yourself through written or spoken English is vital in professional and everyday life. If you worry about making grammatical mistakes you're certainly not alone. Many people regularly make the same common errors. However, once you are aware of these errors and understand them, you are far less likely to continue making them. If you find that you don't make any of the mistakes in the list, you're doing pretty well.
The serial comma, sometimes known as the Oxford comma, is a comma included before "and" when a sentence includes a list. For example, the phrase "oranges, apples, and bananas" includes the serial comma. Whether or not the serial comma is acceptable really depends on the context. British English tends not to use the serial comma, while American English is more likely to use it.
With various blogs and websites dedicated to the misuse of apostrophes, many people seem to get upset by this one. The most common use of an apostrophe is to indicate some sort of ownership. For example "John's books" has an apostrophe before the "s" after "John" because the books belong to John, but "books" does not have an apostrophe because the "s" indicates plurality, not ownership.
There, They're and Their
Since these three words typically sound the same when spoken, their use in written English can be confusing. In general, "there" refers to a place, "they're" is the shortened form of "they are" and "their" indicates possession. For example, "they're eating their sandwiches over there" includes all three words used correctly.
Your and You're
Another case of homophones (words with the same pronunciation), "your" and "you're" can be confusing because they are difficult to distinguish in spoken English. While "your" is the possessive form, "you're" is the shortened, or "contracted" version of the words "you are" with an apostrophe indicating the joining of the two words.
Its and It's
Yet another confusing case of words that sound the same but function differently when written, "its" and "it's" are commonly confused. While you can often assume that an apostrophe before "s" indicates ownership, in this case the possessive form is "its," without apostrophe. The version with apostrophe, "it's" is the shortened version of "it is," with the apostrophe indicating a contraction.
Fewer and Less
The "fewer" or "less" issue has caused much consternation, particularly with supermarket signage. In general, fewer works with the plural of a word representing something that can be counted, such as "fewer apples." You can use "less" in cases where something can't be counted, such as a mass or abstract noun, for example "less fun." Possible exceptions include uses of "less than" with numerical measurements.
When you place sections of text in quotation marks, you will often have to include punctuation. Whether or not to place punctuation inside or outside quotes, when you need a punctuation mark at the end of the quoted text, is the subject of much debate. House styles and conventions vary, but in general, UK English puts full stops and commas outside the quotes, while US English places them inside quotes.
Me, Myself and I
Many people struggle to figure out whether to use "I" or "me," with "myself" only adding to the confusion. The word "I" indicates that you are the subject, which typically means you are carrying out some action, as in "I walked home." With "me," you are the object, as in "he kicked me." The word "myself" tends to be most sensibly used for the object noun when you are both subject and object, as in "I hurt myself."
A modifier is a word or phrase that modifies another part of a sentence. Placing a modifier in the wrong part of a sentence can change or confuse its meaning. For example, "only I ate the cakes" and "I only ate the cakes" have different meanings, determined by where the modifier "only" is placed. Prepositions and preposition phrases are often responsible for modifier confusion so should be placed with extra care.
Either, Or, Neither, Nor
These words work in pairs, with "either" and "or" working in conjunction and "neither" and "nor" also working together. While you will see "neither" appearing correctly without "nor," "nor" should typically not be used without an accompanying "neither." Using "neither" and "nor" is a way of joining words or concepts together in negative structures, such as "I have neither money nor power."
Subject Verb Agreement
If you can't remember, or were never taught traditional grammar concepts such as subjects, objects, verbs and the other parts of speech, you may understandably struggle with subject verb agreement. A reliable rule of thumb is that a plural noun should be matched with a plural verb, and a singular noun with a singular verb. For example, "the dog smells the food" includes singular subject and verb, while "dogs smell funny" uses plural for both.
Which and That
Like most grammatical rules, choosing between "that" and "which" involves looking at the sentence context. In some cases you can use either. In general, "which" refers to all of whatever is being referred to, while "that" refers to a subset or particular instance of what is being referred to. For example, in "the animal, which was in the cage," the "which" refers to everything in the previous clause. In contrast, in "the animal that was in the cage" implies that the particular animal in the cage is being referred to, with other animals possibly present, but not in the cage.
May and Might
You can use "may" and "might" interchangeably in many contexts. If you refer to something that didn't happen, "might" would normally be more appropriate, for example "that might have hurt someone." Both "may" and "might" indicate a lack of certainty, but "may" is generally interpreted as expressing more certainty than "might."