big, large, wide
She has a very wide group of friends.

little, select, small
The president met with a select group of senior negotiators.

coherent, cohesive, homogeneous, tight, tight-knit, tightly knit
The strangers who came together for the course soon became a cohesive group.

diverse, heterogeneous
organized
minority
Disabled drivers are an ever-growing minority group.

dominant, powerful
cultural, demographic, ethnic, racial, social
family
The animals live in family groups of 10–20 individuals.

age, peer
young people in this age group
He started smoking because of peer-group pressure.

discussion
a discussion group that meets once a month

research, study
self-help, support
focus
business, consumer, student
action, advocacy (esp. AmE), interest, pressure, special-interest
Local parents have formed an action group to campaign for better road safety.

working
rebel, splinter
A few members of the party broke away to form a splinter group.

extremist
hate (esp. AmE)
terror, terrorist
church, religious
conservation, environmental
theatre/theater
book, reading
youth
pop, rock
blood
What blood group are you? (BrE)

comparison, control
muscle
user

create, form, found, organize, set up, start
constitute
head, lead, manage, run
represent
become a member of, join
leave
He left the group last year to pursue a solo career.

form
The group formed back in 1992.

split up
The group has split up and re-formed several times with different musicians.

comprise, consist of, include

leader, member
activity, discussion, work
photo
hug

as a group
The gorillas go foraging for food as a group.

in a/the group
There are fifteen of us in the group.

within a/the group
Within a group, each individual had a definite status.

group of
a group of young mothers

divide sb/sth into groups
We divided the class into small groups.

closely
broadly, loosely
thematically
Works in the exhibition are grouped thematically.

together

according to, by
Eggs were grouped according to size.
The children were grouped by age.

around, round (esp. BrE)
They sat grouped around the fire.

in, into
These stories can be loosely grouped into three types.

with
The England team was grouped with Uruguay and Holland.

group sth under a heading
The names were grouped under four different headings.