You can find the meaning of "cheap" easily in a dictionary. What you may not find there is how to use such a simple word correctly in everyday life. I hope to introduce the connotation of some English words.  Let's start with the word "cheap."

If you have bought something at a good price, say while the store is having a sale, you might tell a friend: "You should go buy one, too. It's cheap."

A native speaker may wonder what you meant by that.

By saying "It's cheap" you unintentionally implied that the goods is of low quality.

The correct expressions in this case can be:
1) The price is really good.
2) It's a pretty good deal.

To learn more about connotation, check out wikipedia:
"Usage A stubborn person may be described as being either strong-willed or pig-headed. Although these have the same literal meaning (i.e. stubborn), strong-willed connotes admiration for the level of someone's will, while pig-headed connotes frustration in dealing with someone.It is often useful to avoid words with strong connotations (especially disparaging ones) when striving to achieve a neutral point of view. A desire for more positive connotations, or fewer negative ones, is one of the main reasons for using euphemisms."

For fun, do you know the Chinese translation of "cheap" in the following example?
JoAnn says to me: "He is so cheap!"