abside Same as apse.

absidiole Same as apsidiole.

absolute humidity The mass of water vapor per unit volume of air.

absolute pressure The sum of the gauge pressure plus atmospheric pressure.

absolute volume 1. Of a granular material, the total volume of the particles, including the permeable and impermeable voids, but excluding the spaces between the particles. 2. Of fluid, the volume which the fluid occupies. 3. The displacement volume of an ingredient of concrete or mortar.

absorbed moisture Moisture that has entered a solid material by absorption and has physical properties not substantially different from ordinary water at the same temperature and pressure. Also see absorption.

absorbency The property of a material that measures its capacity to soak up liquids.

absorbent A material which, owing to an affinity for certain substances, extracts one or more such substances from a liquid or gas with which it is in contact, and which changes physically or chemically, or both, during the process.

absorber 1. A device containing liquid for absorbing refrigerant vapor or other vapors.  2. In an absorption system, that part of the low-pressure side of the system which is used for absorbing refrigerant vapor. 3. That part of a solar collector whose primary function is to absorb radiant solar energy.

absorber plate Same as solar collector.

absorbing well, dry well, waste well A well used for draining off surface water and conducting it underground, where it is absorbed.

absorptance In illumination engineering, the ratio of the absorbed flux to the incident flux.

absorption 1. The process by which a liquid, or a mixture of gases and liquid, is drawn into and tends to fill permeable pores in a porous solid material; usually accompanied by a physical change, chemical change, or both, of the material.  2. The increase in weight of a porous solid body resulting from the penetration of liquid into its permeable pores. 3. The increase in weight of a brick or tile unit when immersed in either cold or boiling water for a stated length of time; expressed as a percentage of the weight of the dry unit. 4. The process by which radiant energy, which is incident on a surface, is converted to other forms of energy. 5. See sound absorption. 6. See light absorption.

absorption bed A pit of relatively large dimensions which is filled with coarse aggregate and contains a distribution pipe system; used to absorb the effluent of a septic tank.

absorption coefficient See sound absorption coefficient.

absorption field, disposal field A system of trenches containing coarse aggregate and distribution pipes through which septic-tank effluent may seep into the surrounding soil.