The basic meaning of class is "homework, class", which can also refer to the specific "one lesson at a time" and sometimes the text. By extension, it can refer to "lessons, experiences" or "examples".

When solving "homework, class", Lesson often uses the plural form; The explanation of "one lesson, one lesson" is usually in singular form; The solutions of "lessons, experiences" and "examples" are countable nouns.

Discrimination of words:

Classes, classes and courses all have the meaning of "class". The difference is:

Class originally refers to people studying the same subject in the same class, which can be extended to students getting together to "attend classes"; Curriculum refers to the homework to be taught or learned in teaching for a period of time, that is, "curriculum"; Class hours refer to the "paragraphs" divided by the course, "one class" or "unit time of each class" in the teaching materials. For example:

There is no class today. There is no class today.

I studied English in middle school for three years. I studied English in middle school for three years.

The new lesson is very difficult. The new lesson is very difficult.