Intensity is a widely-used term, which can mean:

In colloquial use:

• Strength
• Amplitude
• Level

In physics:

• Intensity (physics), power per unit area (W/m²)
• Field strength of electric, magnetic, or electromagnetic fields.

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)

In astronomy:

• Radiance, power per unit solid angle per unit projected source area (W·sr^-1·m^-2)

In seismology:

• Mercalli Intensity, a measure of earthquake impact
• Japan Meteorological Agency seismic intensity, a measure of earthquake impact
• Peak ground acceleration, a measure of earthquake acceleration (g or m/s²)

Other uses:

• In video, intensity means luminous emittance, luminous flux per unit area (lm/m² or lux)
• Exercise intensity is a measure of how much work is done during exercise (% of max heart rate)
• Intensity (novel), a novel by Dean Koontz
  • Intensity (TV movie), a 1997 made for TV movie based on the novel

See also

• Sound intensity
• Brightness