Correct spelling, explanation: the word apartment comes from the French language, in which it had the form appartement, and the Italian language, where it had the form appartamento. In both languages, it referred to private rooms. Today, in modern English, it is a countable noun with a meaning close to the original one.

Definition of apartment:
noun – refers to a few rooms which form a place of living, the British English equivalent is the word flat,
If you want to visit the USA on holiday, you can stay in my apartment for as long as you wish.

Collocations with apartment:
Some common collocations include:
apartment building – a large building with a few apartments,
He lives in a modern apartment building located in the heart of the city.
studio apartment – it is a small apartment with only one room, a kitchen, and a bathroom,
I live alone so a small studio apartment is just enough for me.
bachelor apartment – a small apartment for just one person,
Having graduated from the university, he decided to sell his tiny bachelor apartment and find something bigger.

Incorrect spelling, explanation: when it comes to spelling it is worth noticing that there is a single -p letter in the first syllable. A common mistake made by many English users is to double it, which gives appartment, but this form is wrong so do not use it.

Incorrect spelling

Incorrect spelling

Incorrect spelling