What is the definition of deception?

Hello all, I bring before you this question, I understand deception is an offspring of lying but when does lying become deception?

For example if you tell your child that Santa is real and have them believe in Santa you are lying by telling your child about a person who isn’t real is that deception?
Or you lie to someone to throw them a surprise birthday party or something along those lines, Is that deception?

I am just kind of confused where to draw the line, I understand if you copy on a test and claim the work as your own and your teacher believes that is deception, but I am just confused when does a simple little white lie become deception, or does it only matter when the lie is told in a certain context. Like if you lie in order to benefit yourself is that when it becomes deception?

I am just confused if somebody could give me the definition of deception in plain English in regards to faith it would be greatly appreciated.

-Michael

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