What does the root word non mean?

Answer 1

it means the opposite of whatever the word in front of it is

for example lets say something makes sense , opposite of that would be nonsense

non- 

a prefix meaning "not," freely used as an English formative,usually with a simple negative force as implying mere negationor absence of something (rather than the opposite or reverse ofit, as often expressed by un-1 ): nonadherence;noninterference;nonpayment; nonprofessional.

Answer 2

The root word non- means "not" or "without." It is commonly used to indicate the absence or negation of something.