Do I need to sign 'I' before 'know'?
In ASL, you often don't need to sign 'I' before 'know.' The context, along with a slight head nod, usually makes it clear that you are talking about yourself. You can sign 'I' first if you want to add emphasis.
What is the difference between 'know' and 'don't know'?
To sign 'don't know,' you start with the same handshape at your forehead, but then you turn your hand outward and away from your head while shaking your head 'no'.
Is this the same sign as 'understand'?
While they are related concepts, 'understand' has its own distinct sign, which involves flicking your index finger up near your forehead like a lightbulb turning on. Use 'I know' when referring to possessing facts or information.