HOMOPHONE: each of two or more words having the same pronunciation but different meanings, origins, or spelling, e.g., new and knew.

Since using the wrong homophone can completely change the meaning of your statement, it’s important to make sure you have the right word in mind.
Than vs. Then
Despite their single letter of difference, misusing ” and “then” can change a statement completely. “Than” is the word to use in a comparative statement, like “You’re a better writer today than you were yesterday.” Use “then” when describing a sequence of events, like “Write a good sentence, and then compose a great paragraph.”
To and Too
While “to” and “too” sound the same, remember that the former is while the latter is an adverb. “To” typically means “toward,” while “too” can either mean “excessively” or “also.” For example, you could say, “When you go to the beach, take me too.”
Your vs You're
Though it’s a common mistake, using the wrong version of this word can make your writing look sloppy. “Your” is always a possessive pronoun, so when you use this word, be sure you’re declaring ownership. For instance, you could say, “your book” or “your professional writing sample.” “You’re,” on the other hand, is a contraction of the words “you” and “are.” When using this word, check yourself by reading it with the words “you are” in place of the contraction to make sure it makes sense.
Threw vs Through
“Threw” and “through” may be different parts of speech, but they can be tough to keep straight. The first work in this homophone pair is the past tense of the verb “throw,” or the act of tossing something in the air. “Through,” however, is an adverb that implies movement through space or time. You could say, for instance, “The pitcher threw the baseball through the air like a pro.”Many writers confuse these since the only spelling difference is a single vowel towards the end of the word. 
Stationary vs Stationery
“Stationary” and “stationery,” however, have very different meanings. “Stationary” refers to standing still, while “stationery” refers to cards, paper, or other writing materials. Your stationery may be stationary, but never the other way around.
Seas vs Sees vs Seize
As if two homophones weren’t enough, you will find three spellings of this sound-alike. “Seas” is a noun that describes oceans and other large bodies of water, while the verb “sees” refers to looking or observing. Finally, “seize” means to take control. “She sees the opposing forces seize the seas” demonstrates the unique meaning of all three.
There vs Their vs They're
You’ll also find three of these tricky homophones. “There” refers to a general location or distance. When describing where you parked your car, for instance, you might say, “My car is in the parking lot over there.” “Their” serves as a possessive form for more than one person. When referring to the vehicles belonging to a group of people, for example, you would say, “their cars.” Finally, “they’re” is a contraction of the words “they” and “are.” Whenever you use this term, make sure that what you really mean is “they are.” For instance, you could say, “They’re parking.” If you’re really ready to show off your knowledge of homophones, try out the statement, “They’re parking their car in that lot over there.”
Homophones may sound the same, but their meanings are very different when you use them in writing. Study up on which words you need to use, and when, as many spelling and grammar checkers cannot correct for words that are spelled correctly but used wrong. (Lucky for you Grammarly can!)