Afterglow:

Egress System:                 

Phosphorescent or fluorescent light (also related to extinction time)

The action or right of going out, aplace or means of going out. To exit 

Excitation time:

Time required for saturation with standard D65 illuminant at 200 lux.

Extinction time:

Time required for afterglow to diminish to one masb (0.32 mcd/m2, or about 100 times limit of human perception). (Referred to as the light decay "period" in DIN 67510 standard.)

Fluorescence:

Emission which occurs immediately after excitation ceases, and which decays in picoseconds. Due to excited molecule or atom going directly from excited state to lower energy level.
IESNA RP-16-1996: "The emission of light as the result of, and only during, the absorption of radiation of shorter wavelengths (time scale less than approximately 10-8 seconds)."

The period in which a photoluminescent component is at its maximum glow.

Luminescence:

The emission of light by a material after it has been exposed to some method of excitation. Includes photoluminescence (electromagnetic radiation), cathodoluminescence (electrons), electroluminescence (stationary or varying electric fields), chemiluminescence (chemical reactions), bioluminescence (biological processes), sonoluminescence (acoustic energy), thermoluminescence (temperature changes), radioluminescence (subatomic particles), and triboluminescence (mechanical energy).
IESNA RP-16-1996: "Any emission of light not ascribable directly to incandescence."

Phosphors:

Luminescent materials, consisting of two general groups. The first group (mostly organic materials) have molecules which absorb excitation energy, the molecules enter an excited energy state, and emit radiation as they return to a lower state. The second group (mostly inorganic compounds) derive their luminescence from perturbations in their crystal lattice structure or the presence of foreign atoms (called activators). The activators become ionized, and release their energy when the free electrons combine with the ionized atoms.
Typical inorganic materials are sulphides and oxides or silicates and phosphates of metals such as zinc, calcium, magnesium, cadmium, tungsten, and zirconium. Small amounts (0.01 to 1.0 percent) of metal impurities are added as activators.

Phosphorescence:

Emission that decays slowly (minutes to weeks). Due to excited molecule or atom remaining in a metastable energy state when perturbed by atomic collisions or other causes.
IESNA RP-16-1996: "The emission of light as the result of the absorption of radiation, and continuing for a noticeable length of time after excitation."

Quantum efficiency:

Number of visible photons emitted divided by number of UV photons absorbed. Depends on chemical composition of phosphor, method of construction or deposition, and kind of excitation.