A, a 1. Abbreviation for acre. The more common abbreviation for acre is ac. 2. Abbreviation for ampere(s). 3. Abbreviation for area. In landscape applications, area is often expressed in square feet, square yards, or square meters. 4. In botanical terms, a prefix meaning not; different from; away from; without.

A1 horizon A soil layer that is a subhorizon of the A horizon, distinguishable by its darker color from the rest of the A horizon due to a higher content of organic matter.

A2 horizon A soil layer that is a subhorizon of the A horizon, distinguishable by its lighter color from the rest of the A horizon due to a lack of organic matter because of leaching or eluvia-tion.

A3 horizon A soil layer that is a subhorizon of the A horizon, similar to the A2 horizon, but also transitional to the B horizon, with visually distinguishable changes from either.

AAA Abbreviation for the American Arbitration Association.

AAN Abbreviation for the American Association of Nurserymen (now known as the ANLA).

AAN Standards The American Standard for Nursery Stock, as published by the American Association of Nurserymen (AAN).

AARS Abbreviation for All-American Rose Selections.

AAS Abbreviation for All-American Selection.

abacus A slab or division that forms the uppermost portion of the capital of a column, usually wider than the column.

abandonment A word often used in contract law to describe the failure of both parties to abide by the terms of a contract.

abate Removal of material, usually in making a design or producing a product from wood, metal, stone, etc. In metal work, this may be descriptive of the beating or pounding of a design into the material.

abat-vent Angled members with some space between them in an opening of an exterior wall or fence used for access to light while blocking wind and screening views. See also louver.

abaxial In botanical terms, the side away from the axis.

ABC 1. Abbreviation for aggregate base course. 2. A reference to a type of soil profile. (See ABC soil.) 3. Abbreviation for Associated Builders and Contractors.

ABC soil A mature soil profile that contains the three major soil horizons.

aberrant A descriptive term given to individual plants or species different in some way from the group they are associated with.

abiotic Not living.

abortive In botanical terms, an imperfectly developed portion of a plant.

Abram's law The strength of concrete is directly influenced by the ratio of water to cement.

abrasion The act of wearing away by friction.

abrasive A substance harder than the material it is used against in rubbing or grinding to create abrasive surface friction and wear away the softer material. Examples of useful abrasives are diamonds, carbide steel, metal shot, and sand (as with sandpaper).

abrasive surface A surface that is roughened for safety, such as the front tread of a stair.

abrevoir A space, gap, or joint between stones that is filled with cement or mortar.

abscisic acid A growth-inhibiting plant hormone, which also promotes leaf fall (abscission), the formation of potato tubers, and the change to dormancy in leaf buds.

abscission The natural separation of fruit, leaves, or flowers from a plant at a special area of tissue.

abscission layer The layer of tissue in a plant that facilitates the dropping of fruit, flowers, and leaves that cease to function.

absolute pressure In pumping references, the total pressure above absolute zero.

absorbed moisture Water that has been absorbed into the pore spaces of a solid such as soil or wood.

absorber 1. That portion of a solar collector that collects and absorbs radiant heat energy. 2. A material that collects and holds pollutants such as oil from water runoff, usually within a catch basin or an oil separator. 3. A device used to arrest the shock of water hammer.

absorbing well or dry well or waste well A

well collecting surface waters, providing for the water to be dispensed and absorbed into the ground.

absorption 1. A process by which a gas and/or liquid enters into a solid material. This occurs through pores in a porous solid material. This process is usually accompanied by a chemical and/or physical change of the solid material. 2. The process by which radiant energy is con verted to other forms of energy. 3. The increase in weight of a solid material due to the process described in (1.) 4. The increased weight of a tile or brick when immersed into boiling water or cold water for a determined period of time. This weight change is usually expressed as a percentage of the weight of the dry weight. 5. A process where one substance adheres to the surface of another.

absorption bed An excavation that is filled with coarse aggregate and has a piping system for distribution of septic tank effluent.

ABS plastic or ABS pipe A plastic of acryl-onitrile butadiene styrene often used to make pipe that is resistant to impact, heat, chemicals, and freeze-thaw. It is softer than PVC plastic and usually black.

abut 1. To make contiguous or to make a contact point. 2. In real estate, two properties with a common property line.

abutment The part of a structure such as a bridge or an arch that bears the weight of the span and is usually made of masonry or concrete.

abuttals Those boundaries of one piece of land that are in common with adjacent pieces of land.

abutting joint A joint between two pieces of wood, where the direction of the grain in one piece of wood is at an angle (usually 90°) to the grain in the other.

AC, ac, a-c, a.c. 1. Abbreviation for acre(s). 2. Abbreviation for alternating current.

ACA Abbreviation for ammoniacal copper arsenate. A thorn-like or spike-like protrusion.

acaulescent In botanical terms, a plant or leaf that is without a stem, or appears to be without a stem.

ACC Abbreviation for acid copper chromate.

acetone accelerated erosion The movement of earthen particles in water runoff increased by human activities influencing the land. Activities causing increased erosion include removal of vegetation, loosening of soil, concentrating areas of runoff, or interruption of natural drainage patterns.

accelerator A material or substance added to concrete, grout, or mortar to increase its rate of hardening, and/or decrease its setting time.

access A way of vehicular, pedestrian, or other approach, entry, or exit.

access door A door that provides access to equipment for maintenance, inspection, or repair.

access panel

access panel or access plate A removable panel or plate (usually secured with screws or bolts) in a frame that is usually mounted in a ceiling or wall and provides access to concealed items or equipment. It permits inspection of an otherwise inaccessible area. Wires and/or pipes for irrigation systems or pumps are sometimes concealed behind these panels in buildings.

They are also sometimes designed into park restrooms and pavilions for infrequent access to areas in ceilings or behind walls.

accessibility standards Parameters and recommendations regarding accessibility of handicapped persons to walks, structures, etc. See Americans with Disabilities Act and Uniform Federal Accessibility Standards.

accessible 1. Easily accessed. 2. Reachable by removal of a cover, panel, plate, or similar obstruction. 3. Easily accessed by those disabled in wheelchairs or walkers.

accessible means of egress A path of travel, usable by a person who has impaired mobility, that leads to a public way.

accessory building A building with a secondary use to that of the main building located on the same plot. Refer to local jurisdictional agencies for their definition.

accessory structure A subordinate structure detached from, but located near, a principal building. Accessory structures usually include garages, decks, fences, sheds, etc.

acclivity A slope above; an upward slope.

accouplement Placement of posts, columns, or pillars in sets of two (paired).

accrescent A botanical term, something that increases in size with age.

ACD Abbreviation for an automatic closing device.

ACE Abbreviation for Agricultural Conservation Easement.

acerose In botanical terms, a plant part shaped like a needle or having a needle-like tip.

acetone A highly volatile solvent often used in lacquers, paint removers, thinners, etc.

acetylene acetylene A colorless gas, that when mixed with oxygen, burns at a temperature of about 3500°C; used in welding.

acetylene torch A metal-cutting and welding instrument that operates on compressed acetylene (a colorless hydrocarbon) and oxygen.

achene In botanical terms, a small, dry, one-celled, one-seeded, indehiscent fruit. In technical terms, it does not include those fruits with specialized features such as a samara, caryopsis, nut, or utricle.

achlamydeous A flower without a perianth

(outside envelope, calyx, corolla).

achromatic color White light; a color that does not elicit hue.

ACI Abbreviation for American Concrete Institute.

acicular In botanical terms, needle-shaped.

acid 1. In reference to soil, this indicates a pH below 7.0 (neutral). 2. A chemical substance capable of releasing excess protons (hydrogen ions).

acid copper chromate (ACC) A waterborne salt preservative for wood. Wood must be pressure treated for this preservative to be effective. It is highly recommended by experts as it is odorless, clean, does not leach, and its color can be masked easily when dry by painting or applying a solid color stain. This stain is not only good for preserving wood above grade, but can also be used for preservation of wood to be placed underground.

acid etched A reference to a metallic surface, glass, or concrete that has been treated in an acid bath to provide a rough surface or to remove a portion of its surface.

acidic 1. Soil or water with a pH less than 7.0.

Some only consider acidic to be 6.6 or less. 2. Igneous rocks containing more than 65% silica.

acidity The measure of a substance's pH below neutral (7.0).

acid rain Any rain that contains sulfur dioxide.

acid soil Soil having an acid reaction. It is usually in reference to a soil having a pH value of less than 6.6, but is technically applicable to any value lower than 7.0, which is neutral. These soils are common in areas of high rainfall. The most common cure for highly acidic soils is the addition of lime.

acisculis An old term for a small mason's pick, with a flat face and pointed peen.

ACM Abbreviation for asbestos-containing material. Any material with over 1% asbestos content.

AC pipe Asbestos-cement pipe that was commonly used for buried pipelines. It combines strength with light weight and is immune to rust and corrosion. It is no longer made because of the health hazards associated with asbestos.

acquiescence 1. An act of concurrence by adjoining property owners that resolves a boundary dispute or establishes a common boundary, where the definite or more accurate position of same has not or cannot be defined by survey. 2. The tacit consent of one owner, by not making a formal objection, to what might be an encroachment by an adjoining property owner over a questionable boundary.

acre English or U.S. measurement of area equal to 4840 sq yd; 43,560 sq ft; 0.405 hectare; 4046.85 sq m.

acre-foot 1. A reference to a quantity of water required to cover one acre to a depth of one foot.

active solar energy system

2. A quantity of any material equal to the amount required to cover an acre one foot deep.

acrid Sharply bitter, unpleasantly pungent, or harsh in smell or taste.

acropodium 1. A raised pedestal bearing a statue. 2. The lowest member of a pedestal of a statue.

acrylonitrile butadiene styrene (ABS) A

plastic formulated into piping that is used primarily in landscape work for drainage systems, storm sewers, irrigation systems, and underground electrical conduits. It is softer and much more bendable than PVC.

ACS Abbreviation for actual.

AC soil An immature, incomplete soil profile with only the A and C horizons present, and no B horizon. These young soils commonly develop from alluvium or on slopes.

actinomycetes A group of soil microorganisms intermediate between fungi and bacteria. They may be filamentous much like fungi, and yet produce spores similar to bacteria. They are microscopic in size and are usually the source of the fresh, uniquely pleasant odor of newly tilled soil. They are active in decomposition, especially of cellulose.

activated sludge 1. A recycled, dried product of municipal sewage treatment plants. It has higher concentrations of nutrients than composted sludge with a rating of approximately 6-3-0.5 for primary nutrients. It is usually sold in a dry, granular form as a general-purpose fertilizer that does not burn, and is slow to release its nutrients. The long-term effects of using sewage sludge are still under investigation. Heavy metals such as cadmium may be present in the soil where sewage sludge has been used, and they may build up over time. There are possible negative effects depending on the content and origin of the sludge used. 2. Sewage within aerated wastewater treatment basins and its associated complex variety of living microorganisms. After settling, a portion of this microbial sludge is recycled to influent of the treatment system. Microbes there continue to grow. The remaining activated sludge is removed from the treatment system and disposed of another way.

active earth pressure The horizontal pressure of retained earth in a horizontal direction.

active layer The surface layer in climates where permafrost exists. It is characterized by freezing and thawing.

active open space Land designated or reserved for recreational facilities such as swimming pools, ball fields, court games, picnic tables, exercise courses, playgrounds, ice skating, etc.

active pressure The force exerted by retained earth.

active recreation Athletic activities, or those activities of leisure requiring physical effort and often requiring equipment. This type of activity usually takes place at prescribed places, sites, or fields. It includes such activities as swimming, tennis, other court games, baseball, other field sports, golf, playground activities, jogging, rowing, etc. See also passive recreation.

active sludge A sludge that is rich in destructive bacteria; useful in breaking down fresh sewage.

active solar energy system A system that collects solar energy and distributes that energy by mechanical devices such as fans or pumps that obtain their energy from a conventional source (not from solar energy).

Act of God

Act of God An unexpected event not controllable by human influence.

actual This word is often used in specifying weight amounts of a specific nutrient in a fertilizer to be applied. This can be determined by taking the percentage of the specific nutrient in the fertilizer mix and multiplying it by the weight of the fertilizer being used.

actual start of construction The first placement of a permanent construction fixture on site.

aculeate In botanical terms, prickly or beset with prickles.

acuminate In botanical terms, sharply tapering to a slender point. (Compare with retuse, cuspidate, aristate, emarginate, acute, mucronate, obtuse.)

acuminate leaf tip

acute In botanical terms, pointed, or ending in a point less than a right angle. (Compare with retuse, cuspidate, aristate, acuminate, emarginate, mucronate, obtuse.)

acute leaf base

acute leaf tip

acute angle Any angle measuring less than 90°.

acute arch or lancet arch A sharply pointed arch whose centers are farther apart than the width of the arch.

AD, ad 1. Abbreviation for air dried. 2. Abbreviation for access door. 3. Abbreviation for area drain. 4. Abbreviation for as drawn. 5. A designation of the surface grades of two sides of a piece of lumber, especially plywood. 6. A Latin prefix used in botanical terms meaning to or toward.

ADA Abbreviation for Americans with Disabilities Act.

adapt To make suitable for a particular purpose, requirement, or condition, by means of modifications or changes.

adapter 1. A fitting or part that facilitates different types (copper, PVC, polyethylene, galvanized) or sizes of pipe to be connected together. 2. A device manufactured for the purpose of connecting tubing or equipment (especially electric) that is of different size, connection type, or design.

adaptive use The extensive alteration, restoration, and/or renovation of an existing structure or building so that it will serve a new purpose.

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