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.
hot
Adjective
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Something that is hot is high in temperature.
The sun is very hot.
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Someone who is hot is sexually attractive.
Woah, that woman is hot!
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Something that is hot is very radioactive.
The atoll is the hottest on Earth.
topic
Noun
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A topic is a general idea that someone is speaking (reading, thinking, etc.) about at a specific time.
We were talking about my problems. Don't change the topic.
Our library has books on a wide range of topics.
When you're writing for school, it's important to stay on topic, and not start talking about other things.