The following types are all monomials:

(1) Simple numbers or prescribed symbols, such as 100, pi, 2π, 3π, etc.

② Multiply two numbers, such as 5× 10 expressed by scientific counting method? 3×4, etc.

(3) the product of two letters, such as a×b, ab, ab? ×c？ ，ab？ c？ etc

(4) The coefficient is not the product of 1 two letters, such as -ab, 4ab? X c and so on

⑤ Molecules do not contain letters, such as 1/2, a/3, a? B/π and so on

Please reply if you don't understand anything. O(∩_∩)O Thank you, please take it.