These appear in professional writing constantly and are among the most noticed errors.
affect / effect
- affect is usually a verb: "The delay affected our schedule."
- effect is usually a noun: "The delay had an effect on our schedule."
Memory aid: Affect is an Action.
advice / advise
- advice — noun, ends in an s sound: "She gave me good advice."
- advise — verb, ends in a z sound: "I advise you to wait."
its / it's
- its — possession: "The company changed its policy."
- it's — it is / it has: "It's raining."
If you can expand it to "it is", use the apostrophe. Otherwise do not.
your / you're
Same test. "You're late" = "you are late". "Your bag" = belonging to you.
lose / loose
- lose — to misplace or be defeated: "Don't lose the key."
- loose — not tight: "The screw is loose."
then / than
- then — time: "We ate, then we left."
- than — comparison: "Bigger than before."
Words often mixed at work
- assure (reassure a person) / ensure (make certain) / insure (buy insurance)
- principal (main, or head of a school) / principle (a rule or belief)
- stationary (not moving) / stationery (paper and pens)
- complement (goes well with) / compliment (praise)
Spellcheck will not catch any of these, because both spellings are real words. They have to be known.
