Correct spelling, explanation: reference comes from the Latin language, in which it had the form referre, whose meaning was to carry back and it is close to the contemporary one. The word, however, entered Middle English directly from Middle French. Referre used to be a verb form, which changed to refer in English while reference is a noun.

Definition of reference:
1. noun – it usually refers to a letter with some information about somebody we know or to the fact of mentioning something;
You should provide us with a reference letter from your previous employer.
You shouldn’t have made the reference to her wedding day – you know she doesn’t like talking about it.

Expressions with reference:
Some interesting expressions include:
1. a reference book – a book with facts, e.g. a dictionary or an encyclopedia,
If you’re not sure about it, check it in a reliable reference book.
2. a reference group – a group of people who can provide some information about a larger group,
They used some teenagers from this school as a reference group for their marketing campaign.
3. a credit reference – information about your ability to pay your debts,
Before a bank provides you with a suitable offer, it needs your credit reference.

Incorrect spelling, explanation: a noun reference and a verb refer come from the same word family and it is true that when you want to add an -ed ending to the verb, you need to double the -r letter, which results in referred. Probably due to that rule, some users of English think that the same happens with reference and they make a mistake of spelling it as referrence, which is incorrect.

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling