1. in thermodynamics, one of the three states of matter, solid, liquid, or gas.

2. in an alternating electric current, the definite time relation of the alternations to the rotational position of the alternator. (In a polyphase machine, the phases are separated by 360 electrical degrees divided by the number of phases.)

3. position in a cycle.

4. one conductor of several, each with different electrical phase.

shift of a material or system from one phase to another, such as liquid to gas, liquid to solid, solid to gas. See state.

unit of loudness level. Sound pressure level of a 1000 hertz reference tone, judged by the average listener to be equally loud to the sound being rated. Compare decibel.

adj. capable of generating a voltage as a result of exposure to visible or other radiation.

device that detects or measures electromagnetic radiation by generating a potential at a junction (barrier layer) between two types of material, on absorption of radiant energy. Also known as barrier-layer cell, barrier-layer photocell, boundary-layer photocell, photronic photocell.

properties of physical phenomena, or relationships between the various quantities or qualities which may be used to describe the phenomena, that apply to all members of a broad class, practically without exception.

properties discussed in physics, exclusive of those described under mechanical properties; for example, density, electrical conductivity, coefficient of thermal expansion. Compare mechanical properties.