1. This letter is addresses to someone else, there must be some mistake (mistake refers to .......)

inaccuracy

misprint

fault

error

2. You must try to learn from our mistakes (mistake refers to .......)

fault

inaccuracy

error

Confuse

3. His essay is full of spelling mistakes (mistake refers to .......)

Confuse

Misconception

Misidentify

Inaccuracy

4. Sorry, I mistook what you said (mistake refers to .......)

Misunderstanding

Error

Slip

Misidentify

5. I think you must be mistaking me for someone else (mistake refers to .......)

Misidentify

Error

Inaccuracy

Misprint

6. I admit that I mistook his intentions (mistake refers to .......)

Misidentify

misjudgement

Error

Inaccuracy