illusion
noun uk/ɪˈluː.ʒən/ us/ɪˈluː.ʒən/
C2 [ C or U ]幻觉，幻想
an idea or belief that is not true
He had no illusions about his talents as a singer. 他对自己作为歌手的才华不抱幻想。
I'm under no illusions (= I understand the truth) about the man I married. 我对我所嫁的男人不抱幻想。
My boss is labouring under the illusion that (= wrongly believes that) the project will be completed on time. 我的老板还存有工程能按时完工的幻想。
C2 [ C ]假象，错觉
something that is not really what it seems to be
A large mirror in a room can create the illusion of space. 房间里放面大镜子能给人一种房间很宽敞的错觉。
The impression of calm in the office is just an illusion. 办公室里的平静其实只是种假象。