Then vs Than

"Then" is used for time sequences, while "than" is used for comparisons. Misusing these words is a typical grammatical error.
4°
Affect vs Effect

Knowing the difference between "affect" (a verb meaning to influence) and "effect" (a noun meaning the result) is essential to avoid misuse.
3°
Your vs You’re

Many people confuse "your" with "you're". "Your" is a possessive adjective, while "you're" is a contraction for "you are". Remembering this distinction helps in avoiding common errors.
2°
There vs Their vs They’re

"There" refers to a place, "their" is a possessive adjective, and "they're" is a contraction for "they are". Mixing these up is a frequent mistake.
1°
Its vs It’s

"Its" is a possessive form of "it", while "it's" is a contraction for "it is" or "it has". These are often confused due to similar pronunciation.