Definition of senior

< senility

senior airman >

sen·ior    (snyr) KEY 

ADJECTIVE:

1. Abbr. Sr. Of or being the older of two, especially the older of two persons having the same name, as father and son.
2. Of or relating to senior citizens. See Usage Note at old.
3. 1. Being in a position, rank, or grade above others of the same set or class: a senior officer; the senior ship in the battle group.
   2. Having precedence in making certain decisions.
4. Of or relating to the fourth and last year of high school or college: our senior class.

NOUN:

1. 1. A person who is older than another: She is eight years my senior.
   2. A senior citizen.
2. 1. One that is of a higher position, rank, or grade than another in the same set or class.
   2. A student in the fourth year of high school or college.

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ETYMOLOGY:
Middle English, from Latin, comparative of senex, old; see sen- in Indo-European roots