Grammar mistakes can be quite common, even for native speakers. Here's a list of some of the most common grammar mistakes in English:
Affect vs. Effect: "Affect" is a verb, meaning to influence or cause a change. "Effect" is a noun, meaning the result of something. Example: "The medicine affected his mood, but the effect was temporary."
Complement vs. Compliment: "Complement" means to make something complete or perfect. "Compliment" means to praise someone. Example: "The wine complements the meal nicely." vs. "She complimented his work."
Its vs. It's: "Its" is possessive, meaning it shows ownership. "It's" is a contraction for "it is" or "it has". Example: "The company's profits are increasing." vs. "The company it's profits are increasing."
Principal vs. Principle: "Principal" is a noun, meaning the head of a school or organization, or the main part of something. "Principle" is a noun, meaning a fundamental truth or proposition. Example: "The principal of the school is very strict." vs. "She stands firm on her principles."
There vs. Their vs. They're: "There" is used to refer to a place or to introduce a subject. "Their" is possessive, meaning it shows ownership. "They're" is a contraction for "they are". Example: "Is there a book on the table?" vs. "Their car is parked outside." vs. "They're going to the movies."
Who vs. Whom: "Who" is used for the subject of a sentence, while "whom" is used for the object. Example: "Who are you going to call?" vs. "To whom should I address the letter?"
For more information on grammar rules and exercises, check out our Grammar Resources.