Correct spelling, explanation: the word has its origin in the Old French disappointen. The root is the word appoint, which means to establish, create or come together – it has a connotation with some positive action. The prefix -dis, however, suggests that there is a lack of something and therefore the word disappoint has a negative connotation.

Definition of disappoint:
1. verb – not to satisfy someone’s needs, hopes, wishes, He disappointed his father when he failed another exam.

Disappoint word family:
1. noun – disappointment,
I would never like to be a disappointment to you.
2. adjective – disappointed, usually goes with the preposition with,
I was so disappointed with the movie that I fell asleep while watching it.
3. adjective – disappointing,
Unfortunately, the film was so disappointing that we left before it ended.

Incorrect spelling, explanation: words with double letters often cause a lot of trouble not only to the learners of English but to the native speakers, too. You never know when a double letter appears as you don’t hear it in speech. Therefore omitting one -p in disappoint is quite a common mistake making form disapoint never a correct one).

Incorrect spelling