The word know is primarily used as a verb to express awareness, understanding, or acquaintance with facts, information, or skills. It is often used to convey familiarity with people, places, or things, as well as to indicate awareness of a particular fact or piece of information. Know changes form depending on the tense, and its past tense is 'knew'.

The word no is used to give a negative response or indicate the absence of something. In sentences, it often precedes nouns to negate their presence or comes alone as a reply. It can also emphasize the exclusion of something when placed before a comparative adjective or adverb.

Although know and no may sound identical, their meanings, usages, and grammatical functions are starkly different. Know encapsulates the act of understanding or being familiar with someone or something, functioning as a verb with different forms. On the other hand, no signifies refusal, negation, or the absence of anything and can operate as an adverb, a noun, and a determiner. These two terms are core to effective English communication, and their proper usage is pivotal to expressing clear and precise meaning in both spoken and written contexts.