Englishfor English speakers
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.
variety
Noun
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A variety of things is a group of things that are not all the same.
Americans can buy a wide variety of cheap products at local supermarkets.
This study was conducted over a relatively long period of time and in a variety of settings.
The films cover a wide variety of topics from wars to fantasy.
The teachers use a variety of techniques to help the students understand the material.
We get the information from newspapers and a variety of other sources.
They felt it was important for a variety of reasons.
The shirts are available in a variety of fun colors.
Middle school students participated in a wide variety of activities.
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Variety is the quality of not being the same.
Fruit can add variety to your salads.
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A variety is one kind of something, especially plants and animals.
The shop has 25 tomato varieties.
By 1930, Southerners alone had developed nearly 1,400 unique apple varieties.
of
Preposition
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Made using.
It is a house of cards.
factor
Noun
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A factor is one of a number of things that causes a result.
The main factor in the success of our program is our excellent teachers.