Nouns

(n)senioran undergraduate student during the year preceding graduation
(n)elder, seniora person who is older than you are

Adjectives

(a)seniorolder; higher in rank; longer in length of tenure or service“senior officer”
(s)senior, fourth-yearused of the fourth and final year in United States high school or college“the senior prom”
(s)aged, elderly, older, senioradvanced in years; (`aged' is pronounced as two syllables)“aged members of the society”, “elderly residents could remember the construction of the first skyscraper”, “senior citizen”