olemus
Wiktionary:
3. the main topic of a paper, work of art, discussion, field of study, etc.

näiteid
https://en.wikipedia.org/wiki/Subject_(documents)
https://en.wikipedia.org/wiki/Index_term
https://en.wikipedia.org/wiki/Subject_(music)

arts subjects -- humanitaarained
main subject -- peaaine
sore subject -- valuline teema
subject index -- aineregister
subject matter -- temaatika
subjects -- ainestik

vt ka
- objekt (3)
- teemaväli
- teemaväline