ADJ

limited
chief, main, primary, prime, principal
true
sole
practical, useful
These bars serve no useful purpose
general
a general-purpose cleaning fluid
common
a group of individuals sharing a common purpose
particular, special, specific
dual
a toy with the dual purpose of entertaining and developing memory skills
stated
social
the view that art should serve a social purpose

VERB + PURPOSE

have
lack
accomplish, achieve, fulfil, serve
The scheme achieved its primary purpose, if nothing else

PREP

for a/the ~
I put the chair there for a purpose. a measure introduced for the purpose of protecting the interests of investors
on ~
(= intentionally) He slammed the door on purpose

PHRASES

at cross purposes (= not understanding or having the same aims, etc. as each other)
I finally realized that we were talking at cross purposes
for/with the express purpose of sth
The school was founded with the express purpose of teaching deaf children to speak
for (all) practical purposes
Nominally she is the secretary, but for all practical purposes she runs the place
purpose-built
The cycling events will take place in a purpose-built 20,000-seater stadium
your purpose in life
She saw being a doctor as her purpose in life
put/use sth to (a/ some) purpose
The old mill has been put to good purpose
a sense of purpose
Encouraged by her example, they all set to work with a fresh sense of purpose
strength of purpose
They had great confidence and strength of purpose

ADJ

administrative, business, commercial, domestic, educational, insurance, legal, medical, medicinal, political, research, tax, teaching
You will need to have the vehicle valued for insurance purposes

PREP

for … ~
The drug can be sold for medicinal purposes only
for the ~s of
Let's assume he knows, for the purposes of our argument