Englishfor English speakers
assume
Verb
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If you assume something, you think or believe something without having enough information to know that it's true.
Oh, hello. I assume you're the new student, are you?
If I saw a man dressed all in black, holding a gun, and walking toward me, I would assume that the man is really a dangerous guy and I would run away from him.
I saw your car in the garage, so I assumed you were at home.
a
Determinative
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A is used when the following word could be any of a certain type.
Compare "A book I saw on the shelf" and "The book I gave you yesterday".
a
Noun
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A is the first letter of the alphabet.
The letter "a" comes before "b".
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In some schools, an A is a very high grade.
Ron got an A on his earth science test.
responsibility
Noun
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A responsibility is any action which somebody trusts or expects that another person will do. Responsibilities are normally given or taken.
He took that responsibility upon himself.
Looking after that pet is a big responsibility.