🏁 No is the opposite of yes, now is when you want something done straightaway, and know means you can remember something you’ve learned:
I know that there are no unicorns now.
📲 💻You can use this link to a Google Form to check you can use these words in the right way.
🎯 💻 Want to try a test?
http://www.esldesk.com/common-errors-english/know-now-no

🚦’No’ means you’re saying you don’t want something or it’s a negative answer, e.g. No, I don’t want to go to the concert tonight, or I asked her to stop but she said no. ‘Now’ means something happening at the moment, e.g. The crowd is chanting loudly now, or I want to leave now. ‘Know’ means it’s something you understand in your head, e.g. I know Man Utd are usually a successful football team. It helps if you remember the K in Know stands for the K in Knowledge, which you Know in your head.
🎓 Now can be used as an adverb e.g. I’m going out now, and know is a verb e.g. I know that now. The word ‘no’ is much harder to classify and you’ll find it called an interjection or sentence word, but it can also be used as an adverb e.g. no sooner, an adjective e.g. no fool, and a noun, e.g. her response was a no.