An Etymological Dictionary of Astronomy and Astrophysics

1a) Of or pertaining to something that can exist independent of thought or perception as part of reality. Opposite of → subjective.

1b) Free of any bias or prejudice caused by personal feelings.

2. The → lens or combination of lenses nearest the → object in an optical instrument ( → telescope, → microscope, → camera).
   

3. The → primary mirror of a → reflecting telescope.
   

4. Grammar: Relating to nouns, noun phrases, or pronouns that are the objects of verbs or prepositions.

See also: Adjective of → object.