Correct spelling, explanation: prevention is an English word that comes from the Latin form praevenire, which joins two other Latin words – prae and venire. The former one meant before while the latter one meant come so the meaning of praevenire was to precede or hinder. Prevention first appeared in late Middle English in the form of a verb whose meaning was an act of anticipation.

Definition of prevention:
1. noun – the act of not allowing something to happen,
I think that the best crime prevention method is to make the citizens aware of the consequences of breaking the law.

Expressions with prevention:
A few common phrases with prevention include:
1. prevention is better than cure – means that it’s better not to let something bad happen than deal with the consequences later,
Remember that prevention is better than cure so if you don’t want to spend a fortune on medicines in the future, start to change your lifestyle habits now.
2. cancer prevention – methods that will help you avoid getting cancer,
Doing sports is one of the cheapest and most effective cancer prevention methods.
3. prevention program – measures which are introduced in order to stop or avoid some problems,
Hand sanitizer will be placed in every room of the building as a part of our prevention program.

Incorrect spelling, explanation: prevention is an English noun, which joins the verb prevent with the -ion, which is a typical ending for nouns. Nevertheless, many English users make it longer and spell prevention as preventation, which is incorrect.