# 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 R
^{n}is the set of all vectors v in R^{n}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}= A^{T}. **Orthogonal Set of Vectors**- A set of vectors in R
^{n}is orthogonal if the dot product of any two of them is 0. **Orthonormal Set of Vectors**- A set of vectors in R
^{n}is orthonormal if it is an orthogonal set and each vector has length 1. **Orthophospheric Acid**- Another name for Phosphoric Acid.