Science terms starting with O

286 terms

O-ring A rubber seal used around stems of some valves to prevent water from leaking past.
O<sub>3</sub> See ozone
Oakum Loosely woven hemp rope that has been treated with oil or other waterproofing agent; it is used to caulk joints in a bell and spigot pipe and fittings.
OASIS An isolated, fertile tract or green locality in a desert region, made so by the presence of water. See also Palm oasis
Obligate riparian species A species that depends completely upon habitat along a body of water.
Obligate species Restricted to a particular condition of life; for example, dependent on a particular habitat to be able to breed.
obliquity the tilt of the earth's axis of rotation, currently 23.4 degrees.
OBS Observation(s)
OBSC Obscure
Obscuration Any atmospheric phenomenon, except clouds, that restricts vertical visibility (e.g., dust, rain, snow, etc.).
Obscuring Phenomena Any atmospheric phenomenon, except clouds, that restricts vertical visibility (e.g., dust, rain, snow, etc.).
Observation (OB-ser-VAY-shun) Closely monitoring a patient's condition but withholding treatment until symptoms appear or change.
Observation Well A hole used to observe the ground-water surface at atmospheric pressure within soil or rock.
Observational network Observational network A group of stations (surface meteorological, upper-air, or other stations) spread over a given area for making regular observations.
Observed Brightness The flux due to a light emitting object measured at the observer (in most cases, at the earth or a satellite).
Obsidian A black or dark-colored volcanic glass.
Occluded Front A composite of two fronts, formed as a cold front overtakes a warm or quasi-stationary front.
Occluded Mesocyclone A mesocyclone in which air from the rear-flank downdraft has completely enveloped the circulation at low levels, cutting off the inflow of warm unstable…
Occupancy Sensor An optical, ultrasonic, or infrared sensor that turns room lights on when they detect a person's presence and off after the space is vacated.
Occupational Safety and Health Act See Occupational Safety and Health Administration.
Occupational Safety and Health Act of 1970 (OSHA) The Williams-Steiger Occupational Safety and Health Act of 1970 (OSHA) is a law designed to protect the health and safety of industrial workers and also…
Occupational Safety and Health Administration (OSHA) One of the U.S. agencies responsible for regulation of biotechnology. The major law under which the agency has regulatory powers is the Occupational…
Occupied Space The space within a building or structure that is normally occupied by people, and that may be conditioned (heated, cooled and/or ventilated).
Ocean Energy Systems Energy conversion technologies that harness the energy in tides, waves, and thermal gradients in the oceans.
Ocean Thermal Energy Conversion (OTEC) The process or technologies for producing energy by harnessing the temperature differences (thermal gradients) between ocean surface waters and that of…
Oceanography The study of the ocean, embracing and integrating all knowledge pertaining to the ocean's physical boundaries, the chemistry and physics of sea water, and…
OCFNT Occluded Front - a composite of two fronts, formed as a cold front overtakes a warm or quasi-stationary front.
ochre stop codon See: stop codon.
OCNL Occasional
Octane enhancer Any substance that is added to gasoline to increase octane.
octane rating (octane number) A measure of a fuel’s resistance to self ignition, hence a measure as well of the antiknock properties of the fuel.
octoploid . An organism, or a tissue whose cells contain eight haploid sets of chromosomes.
OEODM The Office of Equal Opportunity and Diversity Management. Provides a duel role.
oestrogen The generic term for a group of female sex hormones which control the development of sexual characteristics and control oestrus.
oestrous (adj.) See: oestrus.
oestrous cycle The cycle of reproductive activity shown by most sexually mature non-pregnant female mammals. AlteRNA tive spelling: estrous.
oestrus In female mammals, the period of sexual excitement and acceptance of the male. Synonyms: rut, heat. AlteRNA tive spelling: estrus (adj.: estrous).
Off-highway vehicle (OHV) or off-road vehicle Any motorized vehicle designed for or capable of cross-country travel on or immediately over land, water, sand, snow, ice, marsh, swampland, or other…
Off-Peak The period of low energy demand, as opposed to maximum, or peak, demand.
Off-peak energy Electric energy supplied during periods of relatively low system demand.
Off-road vehicle See also Off-highway vehicle
Off-road vehicle (OHV) designations OPEN: Vehicles are allowed without restrictions. LIMITED: Vehicle travel off existing roads and trails would be allowed only for authorized or permitted…
Off-site facility A hazardous waste treatment, storage, or disposal area that is located away from the generating site.
Office of Global Programs The Office of Global Programs (OGP) sponsors focused scientific research, within approximately eleven research elements, aimed at understanding climate…
offset You offset an options or futures position by taking a second position in a contract with identical terms, buying if you sold initially or selling if you…
offshoot Short, usually horizontal, stem produced near the crown of a plant.
Offshore Breeze A wind that blows from the land towards a body of water. Also known as a land breeze.
Offshore Flow Occurs when air moves from land to sea, and is usually associated with dry weather.
Offshore Waters That portion of the oceans, gulfs, and seas beyond the coastal waters extending to a specified distance from the coastline, to a specified depth contour…
Offshore Waters Forecast (OFF) - A National Weather Service marine forecast product for that portion of the oceans, gulfs, and seas beyond the coastal waters extending to a…
offspring New individuals resulting from sexual or asexual reproduction. Synonym: progeny.
Offstream uses Water withdrawn from surface or ground water sources for use at another place.
OFSHR Offshore
Ogee A reverse curve, shaped like an elongated letter S. The downstream faces of overflow dams are often made to this shape. (From the French word Ogive).
Ogee crest The shape of the concrete spillway crest that represents the lower profile of the undernappe of a jet of water flowing over a sharp-crested weir at a…
OH The Office of Hydrology, located in Silver Springs, MD.
OHD Overhead
Ohm The unit of electrical resistance to current flow. The resistance in a conductor in which one volt of potential difference produces a current of one…
Ohm's Law In a given electrical circuit, the amount of current in amperes (i) is equal to the pressure in volts (V) divided by the resistance, in ohms (R).
Ohms A measure of the electrical resistance of a material equal to the resistance of a circuit in which the potential difference of 1 volt produces a current…
Oil Defined as oil of any kind or in any form including, but not limited to, petroleum, fuel oil, sludge, oil refuse, and oil mixed with wastes.
Oil (fuel) A product of crude oil that is used for space heating, diesel engines, and electrical generation.
Oil and gas leasing (on BLM land) The BLM leases oil and gas rights to explore for and produce oil and gas resources from federal lands or mineral rights owned by the federal government.
Oil shale Underground formation of a fine-grained sedimentary rock containing varying amounts of kerogen, a solid, waxy mixture of hydrocarbon compounds.
Oil spill contingency fund A revolving fund for spill control efforts has been authorized in cases where the Federal government has taken over containment and cleanup operations.
Okazaki fragment Replicated DNA fragments formed on the lagging strand in DNA synthesis from a double-stranded template.
Okta Used for the measurement of total cloud cover. One okta of cloud cover is the equivalent of 1/8 of the sky covered with cloud.
OLA Abbreviation for oligonucleotide ligation assay.
Old growth Timber stands with the following characteristics: large mature and over-mature trees in the overstory, snags, dead and decaying logs on the ground and a…
Olfactory bulb A part of the brain involved in detecting and discriminating among different smells.
Oligo Oligonucleotide, short sequence of single-stranded DNA or RNA. Oligos are often used as probes for detecting complementary DNA or RNA because they bind…
Oligodendrocyte (AH-lih-goh-DEN-droh-site) A cell that forms the myelin sheath (a layer that covers and protects nerve cells) in the brain and spinal cord.
Oligogenic A phenotypic trait produced by two or more genes working together. See also: polygenic disorder
oligomer A molecule formed by the covalent joining of a small (undefined) number of monomers . See: polymer.
Oligonucleotide A DNA polymer composed of only a few nucleotides. (See Nucleotide.)
oligonucleotide ligation assay (Abbreviation: OLA). A diagnostic technique for determining the presence or absence of a single nucleotide polymorphism within a sequence, often…
oligonucleotide-directed mutagenesis See: site-specific mutagenesis.
oligonucleotide-directed site-specific mutagenesis See: site-specific mutagenesis.
Oligopotent progenitor cells Progenitor cells that can produce more than one type of mature cell. An example is the myeloid progenitor cell which can give rise to mature blood cells…
oligosaccharide Carbohydrate consisting of several linked monosaccharide units.
Oligotrophic Lake classification used to describe young bodies of water characterized by deep, clear, cold, weedless water that can support fish, such as trout.
OLR Outgoing Longwave Radiation
Omega A term used to describe vertical motion in the atmosphere. The "omega equation" used in numerical weather models is composed of two terms, the…
Omega High A warm high aloft which has become displaced and is on the polarward side of the jet stream.
Omega, Ω The ratio of the average total density of matter to the critical density required to make the universe flat and eventually stop its expansion.
OML An Operations Manual Letter. These serve as updates to policy and procedure for the NWService Operations Manual (WSOM).
Omnivore Animal that eats both vegetable and animal substances.
On-district storage Small water storage facilities located within the boundaries of an irrigation entity, including reregulating reservoirs, holding ponds, or other new…
On-farm Activities (especially growing crops and applying irrigation water) that occur within the legal boundaries of private property.
On-farm irrigation efficiency The ratio of the volume of water used for consumptive use and leaching requirements in cropped areas to the volume of water delivered to a farm (applied…
On-Peak A block of (usually 16) hours in each week-day when demand is at its peak. On-peak definitions for physical electricity vary by North America Electric…
On-Peak Energy Energy supplied during periods of relatively high system demands as specified by the supplier.
On-scene coordinator (OSC) The Federal official predesignated by the EPA or Coast Guard to coordinate and direct Federal removal efforts at the scene of an oil or hazardous…
On-Site Generation Generation of energy at the location where all or most of it will be used.
onco-mouse A mouse that has been genetically modified to incorporate an oncogene, which acts as an animal model for studies of human cancer.
oncogene A gene that normally directs cell growth. If altered, an oncogene can promote or allow the uncontrolled growth of cancer.
Oncogenesis The progression of cytological, genetic, and cellular changes that culminate in a malignant tumor.
oncovirus A class of retroviruses that cause a cell to become cancerous. See also cell, retrovirus, cancer, gene
One Percent Chance Flood (One Hundred Year Flood) Flood magnitude that has one chance in 100 of being exceeded in any future 1-year period.
One Sun The maximum value of natural solar insolation.