pre·req·ui·site 
/ˌpri:ˈrɛkwəzət/ noun
plural pre·req·ui·sites /ˌpri:ˈrɛkwəzət/ noun [count] : something that you officially must have or do before you can have or do something else : requirement — often + for or to ▪ Citizenship is a prerequisite for voting. ▪ The introductory course is a prerequisite for the advanced-level courses. ▪ Having good credit is a prerequisite to applying for a loan.
