Correct spelling, explanation: someone is a commonly used indefinite pronoun. It’s a combination of two words, neither of which should be changed. When spelling it, we must pay attention to both parts. The correct version contains four vowels. It is not entirely clear where the misspelling somone came from, it may be due to pronunciation. Someone is the only correct form.

Definition of someone:
pronoun, a person unknown or not named
Someone once told me to always believe in myself.
I’m not sure if I should trust someone I don’t know.

Collocations with someone:
Some most commonly used collocations include someone else.
My wife’s secretly dating someone else.
Sorry, I mistook you for someone else.

Incorrect spelling, explanation: this noun is a combination of two words: some and one. We should remember to include every letter in the pronoun. That’s why someone is the only correct version and somone is just a mistake. This word may cause some trouble due to the pronunciation: when we say it, the -e becomes silent. Try to remember that each of these pronoun’s parts has two vowels.