Incorrect spelling, explanation: a common mistake made by both native users and learners of English is to double a letter -p in apart, which gives the incorrect form appart. The mistake probably comes from the pronunciation that stresses the syllable with the -p letter and that makes it sound a little stronger. As a result, some users may have a wrong impression that the -p letter is doubled.

Correct spelling, explanation: apart is a word with a wide range of meanings. In English, it functions as an adverb or as an adjective, but it has its origin in Latin a parte, which used to mean at the side. The word also appears in many English collocations, idioms, and phrasal verbs.

Definition of apart:
1. adverb – far from one another, separated,
The shops are only 500 meters apart from each other so you can go to both of them.
2. adverb – in small pieces,
My old desk is falling apart, I definitely need a new one.

Expressions and idioms with apart:
1. tell someone/something apart – to realize the differences between two things or people,
I can’t tell two sisters apart as they look almost the same.
2. grow apart – it’s when a relationship stops being close,
It’s difficult to say why we split, we simply grew apart.
3. be worlds apart – be completely different,
We are worlds apart when it comes to our life goals.