big, complex, complicated, vast
simple
excellent, fascinating, good, interesting
serious
This chapter deals with a very serious subject.

controversial, delicate, difficult, embarrassing, sensitive, touchy
taboo
Work is a taboo subject when we go out for dinner.

closed
I don't wish to discuss it any further—the subject is closed.

different, diverse, various
I read books on different subjects.
books on such diverse subjects as trains and ancient sculpture

chosen
Each candidate has to speak for three minutes on her chosen subject.

favourite/favorite, pet (esp. BrE)
Once he gets onto his pet subject there's no stopping him.

control, healthy, human, normal, research, study, test (all science)
research on human subjects
None of the study subjects altered his or her diet in any other way.

cover, debate, discuss, talk about, touch (esp. AmE), touch on
We touched briefly on the subject.

address, deal with, tackle, treat
I wasn't sure how to deal with the delicate subject of money.

examine, explore, have a look at, investigate, look at, look into, pursue
We want to have a fresh look at the difficult subject of corporate fraud.

approach, bring up, broach, get onto, raise
drop
Let's drop the subject since we don't seem to be able to agree.

stick to
I wish he'd stick to the subject.

get off, wander off
She was supposed to be speaking about sales figures, but she kept wandering off the subject.

bring sb back to, get back to, return to
Getting back to the subject of lighting, does anyone have any suggestions for improvements?

avoid
change, switch (AmE)
Don't change the subject.

arise, come up
The subject of gambling has come up several times recently.

range from sth to sth
Internet courses on diverse subjects ranging from nursing to computers

matter
I like the way she writes, although I'm not interested in her subject matter.

on a/the subject
While we're on the subject of books, has anyone read ‘The Corrections’?

subject of
the subject of the new painting

a range of subjects
We discussed a wide range of subjects.

a variety of subjects
She touches on a wide variety of subjects.

difficult, easy
compulsory, core, main
additional, optional, special
specialist
technical
students of technical subjects

research
art (AmE), arts (BrE), science
academic

take
What subjects are you taking (= studying) this year?

offer
The department offers seven different subjects in all.

choose
study
I have spent a lifetime studying this subject.

teach
those who teach core subjects like English

fail, fail in, pass
She was disappointed to fail in two of her four subjects.

drop
Students are free to drop the subject at age 14.

area
The syllabus is divided into five subject areas.

in a/the subject
He did well in every subject.

a choice of subject, a choice of subjects
His unusual choice of subjects made it harder to find a job.

a range of subjects

be, seem
become
leave sb/sth, make sb/sth
His illness left him subject to asthma attacks.

particularly
frequently, increasingly
potentially
still
At this stage these proposals are still subject to change.

be
Everyone was subject to the whim of the sheikh.

become
remain
make sb/sth
All the priories were made directly subject to the abbot.

entirely
directly