Than vs. ThenHow to use "than" and "then" correctly
Than and then have quite distinct meanings, but because their spellings are so similar, it’s easy to confuse them—like quiet and quite. Just remember that than is used in comparing (more than, less than, etc.), while then is used in referring to a sequence of events (e.g., if…then…):
THAN = COMPARING
THEN = SEQUENCE OF EVENTS
This is another error that’s often easy to catch by simply reading your own writing out loud.
Common Errors in English Usage: Errors in diction and idiom commonly made by native speakers of English
List of Common Errors in English Usage (PDF): Printable version of the complete list
Common Grammar Errors: A list of common errors in grammar (topics like subject-verb agreement and parallelism) as distinct from usage