All 4 Uses of

antecedent
in
The Portrait of a Lady

I was myself so much more antecedently conscious of my figures than of their setting—a too preliminary, a preferential interest in which struck me as in general such a putting of the cart before the horse.†
Chpt Pref. *

The young lady who trod the turf beside him had come from a queer country across the sea which he knew a good deal about; her antecedents, her associations were very vague to his mind except in so far as they were generic, and in this sense they showed as distinct and unimportant.†
Chpt 12

Only as a cover for my ignorance; I don't know his antecedents, his family, his origin.†
Chpt 23

They're both antecedent to choice—elements of one's composition that are not to be eliminated.†
Chpt 10

Definitions:

(1) (antecedent)
something that happened previous to something else; or anything that precedes something
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

More rarely and more specifically, antecedent can take on these specialized meanings:

Grammar: a word or phrase that precedes a pronoun and to which the pronoun refers. In She is the best at math in her grade, the pronoun her refers to the antecedent she.

Logic: a condition in a hypothetical proposition such as If all people are moral, then you are mortal.

Genealogy: All of someone's ancestors.

For less common examples, including one in math, see a comprehensive dictionary.