chief, leading, main
senior
sole
I was the sole representative of the committee.

appointed, designated, elected
authorized, official
field (AmE), international, local, national, regional, state
British, US, etc.
personal
legal
congressional, parliamentary, political
council, government
diplomatic
UN
special
the UN special representative for Cyprus

permanent
the Algerian permanent representative at the UN

military
business, company, corporate, industry, management, marketing, trade
customer-service, sales (also informal rep)
She's a sales rep for sports equipment.

financial, insurance, media, pharmaceutical
his success as a full-time financial representative
a panel of media representatives

employee, labour/labor, union, worker
class, student
community, public
NGO
club, committee
church

appoint, appoint sb (as), choose (sb as), elect, elect sb (as), nominate (esp. BrE), nominate sb (as) (esp. BrE), select, select sb (as)
send
The association is sending representatives to the conference.

consult, consult with, meet, meet with (esp. AmE)
Management are obliged to consult with union representatives about changes to conditions.

discuss (sth) with

attend sth
The negotiations were attended by representatives of several states.

vote

body
The country has a new supreme representative body.

representative for
a representative for international shipping companies

representative from, representative of
representatives from citizens' groups

representative on
a nursing representative on the infection control committee

representative to
representatives to a conference

be, seem
consider sb/sth

highly, very
fully, truly
not necessarily
broadly, fairly, reasonably
a broadly representative sample

widely
Exhibits include a widely representative collection of Greek vases.

statistically
nationally
a nationally representative picture of the employment situation

of
Is this group of people fully representative of the population in general?

Representative is used with these nouns:
assembly, collection, cross section, democracy, example, government, rugby, sample, selection, survey