Englishfor English speakers
in
Preposition
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Used to show that something is inside something else.
The cat is in the box.
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Used to show that someone is at home, or is available.
Is John in?
The Doctor is now in.
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Used to show movement towards the inside.
The rain came in through the window.
the
Determiner
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Used, instead of a, to reference something specific, already known to exist.
Compare "I read a book." and "I read the book."
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Used with a stress, to show that the word following is special.
Are you the John Smith that I went to school with?
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Used with an adjective that acts like a noun to mean all of the people concerned
The poor are always with us.
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Used with superlatives forms of adjectives and adverbs.
You are the best.
chair
Noun
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A chair is a piece of furniture for one person to sit on.
Please, pull up a chair and sit down.
There were six chairs around the table.
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The person who is in charge of a meeting is the chair of the meeting.
The chair opened the floor to questions.
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A chair is a position of professor in a university.
A chair of Mathematics has opened at London University.
chair
Verb
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If you chair a meeting, you are in charge of controlling it.
The meeting was chaired by the head teacher.