Grammar is a complex system of rules that governs our language, and makes our communication clear when we write anything. Rather than go into a treatise about all the many aspects of grammar, I will touch on some of the more common errors people make. Many words sound the same when we say them but often are muddled up when written down. Here is my list of 10 common errors:

1. YOUR, YOU’RE — Both sound the same but are different. Your is a possessive as in Your suitcase is packed. You’re is a contraction meaning You are.
2. THERE, THEIR, THEY’RE — Again, three words that sound the same yet are quite different. There refers to a place — He lives there. Their is a possessive pronoun as in Their house is over there. They’re is a contraction of They are.
3. TO, TOO, TWO — The first two of these are often confused. To is half the infinitive to be and others verbs. It is also a connecting word between related nouns or following a verb or adjective. Examples are: Linda went to the shop to buy two bras. Her friend Sarah went from London to Paris to join her. The shop was adjacent to the school. The second too means also. Sarah came too. The last two, of course, is a number.
4. ITS AND IT’S — These are so often confused and yet are so simple to work out. Its is a possessive pronoun as in The dog wanted its dinner. It’s is a contraction of It is or It has.
5. WOULD’VE/SHOULD’VE — These are both contractions that people mistakenly hear as Would of and Should of. That is wrong. These are contractions of Would have and Should have.
6. AFFECT AND EFFECT — Affect is the verb (The pill affects her balance); Effect is the noun (usually) as in They used sound effects. The exception is in instances such as The law effects a change.
7. YOU not YOUSE — It is common for people to think that if there is more than one person referred to, then they use youse, but that is wrong. It is always you whether you are referring to one you or a whole bunch of you.
8. COMPLIMENT/COMPLEMENT — Another often confused duo. You may compliment someone on their fashion sense, but peaches will complement cream, that is, they go together well.
9. STATIONARY/STATIONERY  — The first of these is the state of being motionless while the second, Stationery, refers to items used in writing such as exercise books, pens, pencils etc.
10. CDs and DVDs and other such plurals — This last one is often seen in stores with an apostrophe before the ‘s’. It is a strange phenomenon that once something is abbreviated, that people think that the plural takes an apostrophe. The apostrophe either refers to it as a possessive or as a contraction and therefore does not apply to plural forms, unless you are avoiding confusion by dotting your i’s and crossing your t’s.

This is a sample of the errors people can make in grammar. I’m sure you can think of many more. There were some I left out as they don’t apply to American spellings, such as practice/practise and licence/license which are separate forms in Australian and British English.