Meaning & use
an open book
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UK/ən ˌəʊpən ˈbʊk/
US/ən ˌoʊpən ˈbʊk/
Meaning
nounidiomfigurative
A person or thing that is easy to understand because nothing is hidden about them.
Grammar: Used after be: she is an open book, with no object.
Patterns
- someone is an open book
Tom is an open book; you always know exactly what he feels.
Her life is an open book, so you can ask her anything.
The mayor says the city budget is an open book.
Common combinations
- be an open book
- With his friends he is an open book.
- like an open book
- She read his face like an open book.
- life is an open book
- Her whole life is an open book online.
- hardly an open book
- The company is hardly an open book about pay.
- not exactly an open book
- He is not exactly an open book about his past.
Synonyms and how they differ
- transparent
- Transparent describes openness in an organization or process, while an open book describes a person or something plain to read.
- candid
- Candid suggests frank speech, while an open book includes showing feelings without words.
- straightforward
- Straightforward describes honest behavior but not necessarily full disclosure of feelings.
Opposites
closed bookmystery
Word family
- open adjective
- not closed or hidden
- openness noun
- the quality of being open
- openly adverb
- without hiding anything
- open-minded adjective
- willing to consider new ideas
Commonly confused: an open book or open-book exam?
an open book vs open-book exam
An open-book exam lets students use their notes; it is a literal use, not the idiom.
Practice
My sister hides nothing, so everyone says she is ___.
Choose one answer.
An open book means easy to read and not secretive. A dark horse is nearly the opposite: someone with hidden talents.
Make it your own
Write a sentence using “an open book”, then check it and compare it with the examples above.
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