1. I went to an academy.

2. I went to academy.
3. I went to Chicago Academy.
4. I went to the academy.
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Students go to a private institute after school to study further. Which expressions do we have to use?

All except # 2 are correct in American English. The British often don't use an article before university, so I assume they may not use an article before academy.

If the name of this academy is well-known among the listners, then, # 4 is best.

Thank you, Sue.

What is the difference between them?

1. I went to school.
2. I went to academy.

Can we use 'private institute' instead of 'academy'?

Knowing when to use an article before a noun is probably one of the most difficult details for ESL students to master. There really isn't a good explanation. It seems to take years of constantly hearing and reading English to learn when we use the article and when we don't.

The best explanation I can give is that "I went to school" is such a common term, that years ago we dropped the article. It isn't wrong to say, "I went to academy." But most native speakers would say "the academy," perhaps because it's not a very common expression.

To properly describe the situation you mentioned, the expressions you can use are:

1. "I went to an academy."

Explanation: In this sentence, the use of the indefinite article "an" implies that you went to any academy, without specifying a particular one.

2. "I went to academy."

Explanation: This sentence is grammatically incorrect. You should use the definite article "the" before the word "academy" to make it grammatically accurate. So, the correct sentence would be "I went to the academy."

3. "I went to Chicago Academy."

Explanation: This sentence indicates that you specifically went to the academy named "Chicago Academy," which is a proper noun.

4. "I went to the academy."

Explanation: This sentence implies that there is a specific academy in the context, but it does not provide any further information about its name or location.