When you overcook dinner or singe your hair with a curling iron, grammar usage should be far from your mind. But these situations may cause you to wonder—is burnt or burned the proper past tense of burn? Both words are acceptable, according to Merriam-Webster, but they serve different purposes.
If your instinct is to say you burned your lasagna when you pull it out of the oven, you'd be grammatically correct. When describing the act burning in the past tense—such as "I burned my finger," or "he burned the firewood"—adding ed to the end of burn is the right way to go. Applying burnt to these situations, on the other hand, feels awkward when spoken aloud or written on the page.
That doesn't mean you should remove burnt from your vocabulary altogether. There is one scenario that calls for it: when the past participle of burn is used as an adjective. If you're describing a noun rather than recounting the act of burning, burnt is the more appropriate option. Food names like burnt cream are good examples of this, as are colors like burnt umber and burnt sienna.
When doubting your skills as an English speaker, remember this rule of thumb: Burned is the past tense of the verb burn, and burnt is a past participle used as an adjective. Both usages are proper words, though, so there's no reason to feel embarrassed about mixing up one with the other. And if you're describing the food you accidentally set on fire a few moments ago, you have bigger problems.
Not all grammar conventions are as logical as burnt versus burned. Here are some common "rules" of the English language you can safely ignore.