Common Mistakes
Commonly confused words
Swap in the expanded form — if "it is" works, use it's; if not, use its.
Why this happens
Confused words sound or look alike but differ in meaning — affect/effect, principal/principle, fewer/less. Spellcheck will not catch them because both are valid English. Context and part of speech decide the choice; mixing them undermines credibility in essays and business writing alike.
See it in a sentence
IncorrectThe new policy will effect every student in the program.
CorrectThe new policy will affect every student in the program.
Teaching note: Affect is usually the verb (influence); effect is usually the noun (result).
IncorrectThere are less applicants this year than last.
CorrectThere are fewer applicants this year than last.
Teaching note: Fewer counts discrete items (applicants); less measures bulk (less time).
IncorrectThe principal reason is cost; we must follow that affect.
CorrectThe principal reason is cost; we must follow that principle.
Teaching note: Principal = main; principle = rule. Affect is not principle.
More examples
Its vs it's; their vs there vs they're — homophone trios need slow proofreading.
Read aloud substituting it is or they are.
Compliment vs complement: she complimented his work; wine complements the meal.
Spelling changes meaning entirely.
Lead (metal) vs led (past tense of lead) vs lead (verb present).
Pronunciation and role clarify.
Than for comparisons; then for time: better than before, then we left.
Then ≠ than.
Quick check
The weather may have an affect on attendance at the outdoor lecture.
Show the fix
The weather may have an effect on attendance at the outdoor lecture. The noun result is effect; affect is usually the verb.
Practice this topic in Wrytesmart
Open the grammar workspace to complete interactive exercises for commonly confused words. You will spot errors, fill blanks, and transform sentences — always with teaching notes that explain the principle, not just the correction.
Master commonly confused words in context
Free to start. Sign in to save progress and get adaptive drills linked to your writing.