Lay vs lie

Here’s another one that’s downright mind-boggling. These one-syllable verbs mean (slightly) different things, despite often being used interchangeably. “Lie” means (in addition to its telling-a-fib definition) to recline or assume a horizontal position. So you “lie” down on your bed to go to sleep. “Lay” means something similar – but it needs an object. What that means is that you’re putting something else down into a horizontal position. So you’d “lay” your sleeping baby into her crib. But, to make matters even more confusing, the past-tense form of “lie” is “lay”. So you’d say, “Right after I lay down last night, I had to get up again to use the bathroom”. As for the past-tense form of “lay,” it’s “laid”. Yup, it’s a lot.
Lose vs loose

Ah, another tricky one that comes up quite a bit. “Lose” and “loose” are both fairly common words, at least compared to some of these other commonly confused words, and they mean different things. If the word you want to use is a verb, you’re most likely thinking of “lose”. “Lose”, with one O, means “to misplace”, “to come to be without”, or “to come off worse in”. You “lose” your keys, and you can also “lose” your balance or your cool. You also “lose” a sports match or a bet.
“Loose” can be a verb, meaning “to release,” as in “They loosed the racehorses before the gun went off”. But this use is very rare and somewhat old-fashioned. “Loose” is most often an adjective. If your clothing is too big for you, it’s “loose”, not “lose”. And if your dog runs away, she got “loose” (or is “on the loose”), not “lose”.
Than vs then

The basic difference between these two is that “than” is a conjunction and “then” is an adverb. But…that doesn’t help too much. “Than” is the word you’ll want to use when you’re comparing things: “I’m faster than you.” “I like this house better than your old one.” You’ll also see this word in the phrase “other than”, which means “except” or “besides”: “Other than the opening scene, I liked the movie a lot”.
“Then” usually indicates time, often in a sequence: “I’m going to the library, and then I’ll meet you at home”. It can also refer to a certain time in the past – “Things were simpler back then” – or in the future – “Great, looking forward to seeing you then!” But it doesn’t have to refer to time. It can also mean “as a consequence”, as in: “If you don’t want to go, then don’t.”