Then: at that time; soon after, next; in addition to. I’ll get the ingredients together, then make the cake.
Than: second thing being compared; other than. John is older than Barry. Fred is a better actor than Mike.
Tale: a story. Paul Bunyan is the protagonist in a tall tale.
Tail: a part of anatomy on some animals and insects. The dog was very happy to see his owner and wagged his tail vigorously. Tail can also mean end or behind. The littlest goose brought up the tail end of the formation. As a verb: The detective was tailing the suspect.
Too: means also. I ordered the artichoke dip appetizer and a raspberry daiquiri too.
Two: a number. Karen and Bill have two children.
To: can indicate motion, direction, purpose and more. He went to the store. The store was to the south of the gas station. He applied primer to the wall before painting it.
Cant: an angle or a secret language. Due to the winds and the waves, the ship was at a significant cant to port†. The thieves discussed their upcoming project in public with no one the wiser because they used Thieves’ cant.
Can’t: a contraction for can not. I’m sorry I can’t go out to lunch today, I have another obligation.
Wont: (pronounced “want”) accustomed to, used to. When he came indoors, he immediately took off his shoes, as was his wont.
Won’t: a contraction for will not. I am sorry but I won’t take that pack of gum.
Peak: summit, the top. Her career reached its peak when she became CEO.
Peek: a quick look. He took a peek at the next student’s answer.
Pique: to excite curiosity. He mentioned the possible salary range in order to pique her interest.
Breathe: is what one does to take in oxygen and expel carbon dioxide using the lungs.
Breath: is what one “takes” to breathe.
Data: the word data is plural. The proper usage is data are not data is. Data is only works with a character from Star Trek: The Next Generation. That Data is singular (in more ways than one.)
Datum: a single item of data. One point on the chart.
A few phrases:
Incorrect: For all intensive purposes. (611,000 Google results)
Correct: For all intents and purposes.
Incorrect: Bounden determined. (77,300 Google results)
Correct: Bound and determined.
Incorrect: Tough road to hoe. (57,100 Google results)
Correct: Tough row to hoe.
†BONUS: Trick to remember which side is port and which is starboard – port and left both have four letters. Port is left when you are facing the front of the boat. A second trick to remember which sides knives, forks and spoons should be on on the table: knife and spoon have five letters each, as does right. Fork has four letters as does left. So knives and spoons on the right, forks on the left!