Intensity

Intensity is a widely-used term, which can refer to:

In colloquial use:
 * Strength
 * Amplitude
 * Level
 * Magnitude

In optics:
 * Radiant intensity, power per unit solid angle (W/sr)
 * Luminous intensity, luminous flux per unit solid angle (lm/sr or cd)
 * Irradiance, power per unit area (W/m2)

Other uses:
 * Value intensity in philosophy and ethics
 * Exercise intensity, a measure of how much work is done during exercise (% of max heart rate)