Or

Or Gate
Logic gate whose output will be a 1 if any of it imputs is at 1.
Orbit
The path of a body in space, generally under the influence of gravity.
Orbit Acquisition
Reception of the telemetry containing the information about the orbital parameters of the spacecraft.
Orbital
A wavefunction that describes what an electron with a given energy is doing inside an atom or molecule.
Orbital Angular Momentum Quantum Number
Also known as Angular Momentum Quantum Number.
Orbital Equation
Also known as Kepler′s first law; The orbit of each planet is an ellipse which has the sun at one of its foci.
Order
Harmonic of the rotational speed of rotating machinery. As an example, in the case of the shaft rotating at 6,000 rpm, the first order component occurs at a frequency of 100 Hz (6,000/60), whereas the third order component would occur at a frequency of 300 Hz.
Order Analysis
Order analysis is simply frequency analysis where the frequency axis of the spectrum is expressed in orders of rpm rather than in Hz or rpm.
Order of Magnitude
A logarithmic unit used to compare the sizes of quantities.
Order of Reaction
The sum of concentration exponents in the rate law for the reaction.
Order Tracking
Tracking the evolution of a specific order as rpm changes.
Ordered Pair
A pair of numbers in which one number is distinguished as the first number and the other as the second number of the pair.
Ordered System
A system with an arrangement belonging to a group with the smallest number (possibly one) of equivalent arrangements.
Ordering
Positioning of host and substitution ions in an ordered, repetitious pattern rather than in a random arrangement.
Ordinal Data
A set of data is said to be ordinal if the values belonging to it can be put in order or have a rating scale attached.
Ordinal Number
A number indicating the order of a thing in a series.
Ordinate
The y-coordinate of a point in the plane.
Ordovician
The geological period from 510 million to 439 million years ago.
Ore
A natural mineral mined and treated for extraction of its components.
Organic Aerosol
Aerosol particles consisting predominantly of organic compounds, mainly C, H, and O, and lesser amounts of other elements.
Organic Chemistry
The branch of chemistry that deals with the properties and reactions of carbon-based compounds.
Organic Compound
Compounds that contain carbon chemically bound to hydrogen.
Organic Light Emitting Diode
A type of LED display made from organic polymers that provides a wide viewing angle, low power and does not require a backlight as do LCD screens.
Organochromic Indicators
Coloured organic compounds that change colour when they chelate different metals.
Orichalchum
A Roman brass that consisted of 80% copper and 20% zinc.

Orientation
Arrangements in space of the axes of a crystal lattice with respect to a coordinate system.
Oriented Strand Board
A building panel composed of long shreds of wood fibre oriented in specific directions and bonded together under pressure.
Orifice
Accurate size opening for controlling fluid flow.
Origin
In Cartesian coordinates, it is the point (0, 0) and located at the intersection of the x- and y-axes.
Original Equipment Manufacturer
Products supplied by the company which first created the product.
Ormolu
An alloy of copper, zinc and tin in various proportions with at least 50% copper.

Ornithopter
A flying machine that is supposed to support itself in the air through the use of flapping wings.
Orthic Triangle
The triangle whose vertices are the feet of the altitudes of a given triangle.
Orthocentre
The point of intersection of the altitudes of a triangle.
Orthogonal
Mutually perpendicular.
Orthogonal Complement of a Subpace
The orthogonal complement of a subspace S of Rn is the set of all vectors v in Rn such that v is orthogonal to every vector in S.
Orthogonal Matrix
A matrix A is orthogonal if A is invertible and its inverse equals its transpose; i.e., A-1 = AT.
Orthogonal Set of Vectors
A set of vectors in Rn is orthogonal if the dot product of any two of them is 0.
Orthonormal Set of Vectors
A set of vectors in Rn is orthonormal if it is an orthogonal set and each vector has length 1.
Orthophospheric Acid
Another name for Phosphoric Acid.