R0 or R00 may refer to.
In classical geometry, a radius of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length.
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.
Zero reference pulse or Zero pulse is an artificially produced pulse in a professional television receiver imitating no radio frequency case for modulation index measurements in analogue TV transmitters.
A zero-rupee note is a banknote imitation issued in India as a means of helping to fight systemic political corruption.
A zero-ohm link or zero-ohm resistor is a wire link used to connect traces on a printed circuit board that is packaged in the same physical package format as a resistor.
In economics, zero-rated supply refers to items that are taxable, but the rate of tax is nil on their input supplies.
Zero-risk bias is a tendency to prefer the complete elimination of a risk even when alternative options produce a greater reduction in risk (overall).