senior

Concise Oxford English Dictionary © 2008 Oxford University Press:
senior /ˈsiːnɪə, ˈsiːnjə/

▶adjective

• 1 for or denoting older people.

  ■ Brit. for or denoting schoolchildren above a certain age, typically eleven.

  ■ US of the final year at a university or high school.

• 2 [postpos.] denoting the elder of two with the same name in a family.

• 3 high or higher in rank or status.

▶noun

• 1 a person who is a specified number of years older than someone else: she was two years his senior.

• 2 a student in one of the higher forms of a senior school.

• 3 (in sport) a competitor of above a certain age or of the highest status.

• 4 an elderly person, especially an old-age pensioner.

– derivatives
seniority noun.

– origin ME: from L., lit. ‘older, older man’, compar. of senex, sen- ‘old man, old’.