big, good, greater, huge, large, major, significant, substantial
We spent a good part of the day rehearsing.
The greater part of the building has been refurbished.

minor, small
equal
Cut it into four equal parts.

important, main, principal
basic, central, critical, crucial, essential, fundamental, key, necessary, vital
integral, intrinsic
interchangeable
best, worst
The worst part was having to wait three hours.

early
In the early part of his career he worked in India.

latter
the latter part of the century

first, last, middle, second
upper, uppermost
the upper part of the spine

lower
inner, outer
anterior (technical), front
back, posterior (technical)
northern, southern, etc.
remote
different, distinct, various
separate
inseparable
component, constituent
Break it down into its constituent parts.

body
difficult, hard, tough, tricky
I gave up once I got to the hard part.

easy
fun
Now comes the fun part.

scary
funny
sad
The sad part was that he didn't really care.

interesting

comprise, constitute, fall into, form
The book falls into three distinct parts.

break sth down into, divide sth into, split sth into

in part
Your salary depends in part on your qualifications.
The movie is good in parts.
a serial in four parts

part of
Part of me wants to stay and part of me doesn't.

the parts of the body
foreign parts (esp. BrE)
They're always off to foreign parts.

private parts (= sexual organs)

replacement, spare
Where can I get spare parts for my bike?

auto (esp. AmE), automotive (esp. AmE), car, motorcycle
moving

manufacture
assemble

parts dealer, parts maker, parts supplier
an auto parts maker

number
The adaptors being recalled contain the part number 02K65 on their labels.

big
bit, small, walk-on
speaking

act, have, play, take
sing
Annette Markert sings the part of Medea.

learn
fit
Walken stars as Shannon and he fits the part well.

in the part
He's very good in the part.

part of
She played the part of Juliet.

act the part, dress the part, look the part
He acts and dresses the part of a gentleman.
He was a pirate in the school play and certainly looked the part.

big, huge, leading, major
Luck played a big part in it.

minor
central, significant, vital
active

have
He had no part in the scam.

do, play, take
She did her part in bringing them back together.

part in
They took little part in the discussion.