Englishfor English speakers
assume
Verb
—
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.
an
Determinative
—
An (or a) is used when the following word could be any of a certain type.
I just ate an apple.
It is indeed an honor to have met you today.
obligation
Noun
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An obligation is a duty, something you must do.