<em>Know</em> is a verb meaning to have information or be familiar with something: 'I know the answer.' <em>No</em> is the negative word — the opposite of yes, or a way of saying not any: 'No, thanks' and 'There's no milk left.' The silent K is the only thing separating them in speech.
The core difference
These two are pure homophones: identical in sound, unrelated in job. Know always acts as a verb, so it needs a subject doing the knowing. No is either a refusal or a determiner meaning not any, and it never functions as a verb.
Using each one
- Know (verb): I know her from school. Do you know what time it starts? He knew the risks.
- No (refusal): No, I can't make Thursday.
- No (not any): There's no reason to panic. She had no idea.
Two quick tests
Swap in 'understand' or 'am aware of'. If the sentence survives — 'I understand the answer' — you want know.
Swap in 'not any'. If that works — 'there's not any milk' — you want no.
One of the two will fit and the other will produce nonsense, which makes this an unusually reliable check.
The memory trick
Know and knowledge begin with the same silent K, as do knew and known. If the word belongs to that family of thinking and understanding, it keeps the K.
Where it actually goes wrong
Almost nobody confuses the meanings. The errors are typing errors, and they cluster in a few phrases:
- 'no' for 'know' in questions: 'I don't no' should be 'I don't know.'
- 'know' for 'no' before a noun: 'know one turned up' should be 'no one turned up.'
- 'in the know' — a fixed phrase meaning informed, and one of the few places know works as a noun-like element.
Note that no one is two words in standard British and American English. Noone is not accepted; no-one with a hyphen appears in British writing and is acceptable, though the unhyphenated form is more common in edited prose.
Also useful: know is not normally used in the continuous. Write 'I know' rather than 'I am knowing', even though many other verbs allow it.
Frequently Asked Questions
Is it 'I don't know' or 'I don't no'?
'I don't know.' The sentence needs a verb after 'don't', and 'no' cannot serve as one. The same applies to 'you never know' and 'who knows'.
Is it 'no one' or 'know one'?
'No one' — meaning nobody. 'Know one' only makes sense in a sentence like 'I know one person who has read it', where 'one' is a counted thing.
Why does 'know' have a silent K?
The K was pronounced in earlier English and stopped being sounded over time, but the spelling stayed. The same happened in 'knee', 'knife' and 'knot'.