Prerequisite (noun)

1. A condition or requirement that must be met before something else can happen or be done.
2. A thing that is needed as a prior condition for something else to occur.

Origin:

From the latin prae- ("before") + requisitus ("require.d")

Examples:

1. A high school diploma is a prerequisite for enrolling in a university.
2. Fluency in a foreign language is a prerequisite for many international jobs.
3. Passing the driving test is a prerequisite for obtaining a driver's license.
4. Completing the prerequisite coursework is necessary before enrolling in the advanced class.
5. Having a certain level of fitness is a prerequisite for joining the army.