Children's Illustrated Dictionary.

a b c d e f g h i j k l m n o p q r s t u v w x y z

only
adjective
without any others.
He’s the only person
wearing green.

only
adverb
1 just.

There were only a few beads
left in the box.
2 no more than.
Only five of us went
to the park.

open
adjective

1 not closed or shut, so
that people or things can
go in and out.

Open car doors.
N opposite shut
2 with plenty of space,
or not closed in.
Open fields.

opera
operas noun
a musical play where
the words are sung instead
of spoken.

operate

operates operating operated

verb

1 to work a piece

of machinery.

You must be careful when

operating machinery.

2 to perform surgery

in a hospital.

operating adjective

operation noun

opinion

opinions noun

a person’s belief or judgment

about something.

Who is the best football player,

in your opinion?

opponent

opponents noun

someone who is on

the opposite side in a fight

or competition.

Chess opponents.

opportunity

opportunities noun

a chance, or a suitable time

to do something.

He had the opportunity to go

to Europe for a year.

oppose

opposes opposing opposed verb

to argue or fight against

someone or something.

They opposed the decision to

close the park.

opposition noun

opposite

adjective

1 on the other side.

He saw his friend on

the opposite side of the river.

2 completely different.

Tall is the opposite of short.

opposite noun

optician

opticians noun

a person whose job is to test

peoples’ sight and to sell

eyeglasses and contact lenses.

N say op-tish-un

optimistic

adjective

expecting or hoping that

things will go well.

Optimistic about the future.

N opposite pessimistic

optimism noun

option

options noun

a choice.

You have several options: you

can travel by car, train,

or plane.

optional adjective

orangutan

orangutans noun

a large ape that lives

in tropical forests in

Southeast Asia. Orangutans

eat mainly fruit, but also eat

leaves, bark, and birds’ eggs.

They live in nests called

platforms, which they

build in trees.

N say or-rang-a-tang

orbit

orbits orbiting orbited verb

to move around a planet,

a moon, or the Sun in space.

The Earth orbits the Sun.

orbit noun

orchard

orchards noun

an area of land where fruit

trees are grown.

They were picking apples

in the orchard.

orchard

orange

oranges noun

1 a color made by

mixing red and

yellow together.

opera singer

2 a juicy fruit with

a tough skin.