makeshift, temporary
day (AmE), holiday (BrE), sleepaway (AmE), summer
basketball, football, music, etc. (all esp. AmE)
The kids were at basketball camp most of the summer.

scout
base
The mountaineers set up their base camp at the foot of the mountain.

Gypsy, travellers' (BrE)
army, boot, military
training
rebel, terrorist
fishing, hunting (both esp. AmE)
mining

establish, make, pitch, set up
They established a base camp by the river.
We pitched camp just outside the woods.

be located
break, strike
We broke camp early the next morning.

leave
attend, go to
There are opportunities for children to attend summer camps.

attack, destroy, raid
Militants raided an army camp.

fire (usually campfire)
We sat around the campfire.

site (usually campsite)

at (a/the) camp
The children are spending a week at a summer camp.

concentration, detention, internment, labour/labor, POW, prison, prisoner-of-war, re-education
death, extermination
transit
refugee
the appalling conditions in the refugee camps

be sent to
enter
liberate

inmate
guard
survivor
concentration camp survivors

in a/the camp
She spent five years in a prison camp.

hostile, opposing, rival (esp. BrE), warring
ideological, political
armed
The region split into two armed camps.

divide into, split into

in a/the camp
people in both main political camps

have a foot in both camps (= show loyalty to two different groups)
He can unite the party because he has a foot in both camps.