1. School is a place where people learn things.

2. School is a place where people learn many subjects.

3. School is a place where students learn many things.

4. School is a place where students study subjects.

5. School is a place where people can learn many things.
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Are they all grammatical? Which ones are good definitions of 'school'?

All are fine, yes!

All are correct definitions of "school" -- and sometimes we even use the word "school" when referring to a student who is in college or university.

"What school does he go to?"
"He's at Rice."
[Rice University is in Houston, TX.]

All of the sentences are grammatically correct. However, not all of them are equally good definitions of "school." Let's analyze each sentence:

1. This sentence is a basic definition of school, stating that it is a place for learning. It is a simple and accurate description.

2. This sentence is similar to the first one but specifies that people learn many subjects in school. It emphasizes the breadth of knowledge that can be acquired in a school setting.

3. This sentence identifies school as a place where students learn many things. It focuses on the students' role in the learning process and highlights the wide range of knowledge they gain.

4. This sentence describes school as a place where students study subjects. While studying is undoubtedly a significant aspect of learning at school, it doesn't encompass all forms of learning, such as hands-on experiences, group projects, or practical applications of knowledge.

5. This sentence is a general statement that people can learn many things at school. It doesn't provide specific details about what or how people learn, but it acknowledges the potential for diverse learning opportunities.

Overall, 1, 2, and 3 can be considered good definitions of "school" because they capture the essence of what a school represents – a place of learning, encompassing various subjects and fostering student knowledge.