Correct spelling, explanation: the origin of the word separation can be found in the Latin word separare, which could be translated as to pull apart. Later, the word appeared in Old French, too, and then, in the 14th century, it finally entered English. Today, the word separation functions as a noun.

Definition of separation:
1. noun – when two things or people are separated;
He gets good money while working abroad, but long periods of separation from his family are difficult to deal with.
2. noun – a legal arrangement, according to which married people stop leaving together;
As a result of separation, she moved with their kids to her mother in London.

Collocations with separation:
Some typical collocations with separation include: long separation, complete separation, separation between;
The worst aspect of the two-month hospital treatment was a long separation from my kids.
A complete separation from your tormentor is the only way to get yourself free.
The separation between a mother and a father is always very difficult to understand for the kids.

Incorrect spelling, explanation: the word separation has a rather simple spelling, however, a common mistake is to spell it with the -e letter in the middle of the word, instead of -a, which results in an incorrect form seperation. It is wrong, though, and the only correct spelling is separation.