Learn grammar rules.

Meaning: This means to study the rules of grammar in order to improve your language skills. It's like saying, Make an effort to learn the rules of grammar to communicate more effectively.

Choice of Words: Learn is a verb that means to gain knowledge or understanding of something. Grammar is a noun that refers to the set of rules that govern the structure of a language. Rules is a plural noun that refers to the principles or regulations that guide behavior. When you put them together, "Learn grammar rules" is an instruction to study the rules of grammar.

Alternative Expressions

Related Expressions