These are common mistakes that you can avoid if you understand the correct usage. Use this list as a cheat sheet.
Which & That
Use “that” for information that is essential to the sentence.
Use “which” for extra details set off by commas. If you can remove the clause and the sentence still makes sense, use “which.”
Nobody likes a dog that bites.
A salad, which is low in fat, is a good diet food.
Two words. All the time. No exceptions.
Lay & Lie
Use “lay” to place an object: Please lay the pencil on the table.
Use “lie” to recline: I will lie on the couch for a while.
“Lay” is also the past tense of “lie.”
The cat lies silently.
Yesterday, the cat lay silently for a few hours.
Good & Well
“Good” is an adjective, describing a noun: I am good.
“Well” is an adverb, describing a verb: I am doing well.
Affect & Effect
“Affect” is a verb: How does the stock market affect your savings?
“Effect” is a noun: What is the effect of inflation on your bills?
Less & Fewer
Use “fewer” to describe a smaller number of individual things: This check out line is for customers with 10 items or fewer.
Use “less” to describe a smaller quantity of something: This store carries less products than the other store.
Complement & Compliment
“Complement” with an “e” is a form of the word complete: She used a red hat to complement the outfit.
“Compliment” with an “i” is to praise: I wanted to compliment her outfit.
Emigrate & Immigrate
Use “emigrate” when speaking of leaving a country: emigrate from.
Use “immigrate when speaking of coming to a country: immigrate to.
Principle & Principal
Principle: a rule or standard.
Principal: A leading figure or role. (The principal of the school is your “P-A-L”.)
All ready & Already
Use “all ready” to mean prepared: I’m all ready to go to the park.
Use “already” to mean previously: I’ve already been to the zoo.
Hopefully this cheat sheet will help you avoid these common mistakes in the future.