THE IDIOM COLLECTION LEARN & PRACTISE
An open book
Understand the meaning. See it in context. Make it yours.
01 / UNDERSTAND
Meaning in plain English
A person whose thoughts and feelings are easy to understand.
02 / SEE IT IN CONTEXT
The expression in a sentence
- You can always tell when I am excited; I am an open book.
03 / CHECK YOUR UNDERSTANDING
Quick idiom quiz
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Can you recall the expression?
Complete the example using the expression from this lesson.
You can always tell when I am excited; I am ________.
Show the answer
An open book — A person whose thoughts and feelings are easy to understand.
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Make it yours
Write one sentence using “An open book” about your own life.
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Does your sentence match this meaning?
A person whose thoughts and feelings are easy to understand.
Compare: You can always tell when I am excited; I am an open book.
Check the spelling and how the expression fits the sentence. Your example can be different.
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GO DEEPER
More ways to understand and use it
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When to use it
Use it conversationally when someone shows how they feel clearly or shares their thoughts openly. It is often friendly rather than critical.
More examples in context
- Her face is an open book whenever she hears good news.
- He described his brother as an open book who never hid his disappointment.
Usage note
“An open-book exam” is a different term for an exam in which reference materials are allowed. Being an open book does not mean someone must share private information.
A short conversation
A: How did you know I liked the idea?
B: You are an open book. You smiled as soon as I mentioned it.
A: I suppose I was not hiding my excitement.
One more practice question
Who is an open book?
A. Someone whose thoughts and feelings are consistently impossible to guess.
B. Someone whose feelings are easy to read.
Check your answer
B. The person’s emotions or thoughts are easy to understand.
Related lessons
Meaning and usage checked against Cambridge Dictionary. Explanations, examples and conversation are original.