Passed and past sound alike in many varieties of American English, but they do different jobs in a sentence. That

If you are unsure about stationary vs stationery, the difference comes down to meaning and spelling. Stationary describes something that

The difference between principal vs principle can be confusing because the two words sound exactly alike in standard American English,

Accept vs except can be confusing because the two words look and sound similar, but they have completely different meanings

Choosing between that vs which can be confusing because both words can introduce information about a noun. The difference becomes

Good vs well is a common grammar question because the two words are closely related but usually perform different jobs