Englishfor English speakers
a
Determinative
—
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.
tube
Noun
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A tube is a long object with a hole from one end to the other. The ends may be closed or open.
The high pressure forces the water through the tube.
Toothpaste comes in a tube.
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The Tube is the underground train system in London, England.
tube
Verb
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If you tube, you float on an inner tube.
We went white-water tubing on the Yukon River.
of
Preposition
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Made using.
It is a house of cards.
mustard
Noun
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Mustard is a yellow sauce which can go on hotdogs, etc.
—
A dark yellow colour, the colour of mustard.