illusion, disillusion and disillusionment

illusion

 noun

/ɪˈluːʒn/

 from Latin illusio(n-), from illudere ‘to mock’, from in- ‘against’ + ludere ‘play’.  ill + us + ion

1 [countable, uncountable] a false idea or belief, especially about somebody or about a situation

 under the illusion that… She's under the illusion that (= believes wrongly that) she'll get the job.

 illusion about something The new president has no illusions about the difficulties facing her country (= she knows that the country has serious problems).

I have no illusions about her feelings for me (= I know the truth is that she does not love me).

Her father is mentally ill. I don't feel he distinguish between illusion and reality.

It's not a good time to have illusions.

disillusion

/ˌdɪsɪˈluːʒn/

Verb

 see dis- + illusion.

​disillusion somebody to destroy somebody’s belief in or good opinion of somebody/something

I hate to disillusion you, but not everyone is as honest as you.

Unreasonable apartment prices disillusioned residents about the present government.

disillusion

 noun

/ˌdɪsɪˈluːʒn/

(also disillusionment)

[uncountable, singular]

​disillusion (with something) the state of being disillusioned

There is growing disillusion with the political system.

disillusion with the institution of marriage

See also

illusion, disillusion and disillusionment · Everyday English