What is the difference between fraud (verb) and defraud (verb)? Yes, they are both synonyms, but I wish to find out with the small difference of meaning they have.
In Spanish as well there are two similar words, the difference of which is not very clear for me: mentir y enganar.
I suppose it's similar to russians' врать и обманывать.

Question

What is the difference between fraud (verb) and defraud (verb)? Yes, they are both synonyms, but I wish to find out with the small difference of meaning they have. 
In Spanish as well there are two similar words, the difference of which is not very clear for me: mentir y enganar.
I suppose it's similar to russians' врать и обманывать.

Answer

Fraud is not a verb, it is a noun.

Answer

Like the others said, it's a noun vs verb. Here's some more info about how I would understand it:
 
"To commit fraud" --> "совершить мошенничество" "Мошенник совершил Мошенничество." "Для совершения мошенничества."

"To defraud" or: cheat, deceive, trick, generally-->  "обьманыват"

In English, generally, 'fraud' is a legalistic term although it can be used generally to describe deception, cheating, lying, false misrepresentation, scamming, etc.

Also, a person can be a fraud (i.e. a 'fake' or someone who misrepresents themself). This can be used for criminals/scammers, but is more often used to describe a person who is deceiving themselves or others due to some kind of inferiority complex or personality problems.

Answer

As Charlie mentioned, fraud is a noun and defraud is a verb.

A person "commits fraud", and "defrauds" someone.