J A Townsend Peter Murray-Rust Jim Downing Sam Adams Nick England Type of each unit. In general there is one SI unit for eachunitType. The term maps closely onto Quantity. However there can be many quantities which share the same unitType. Thus enthalpy and free energy are distinct concepts and quantities but share the same unitType (energy) unitType represents a computable quantity and should not be used loosely for quantity. unitType does not currently point to the corresponding SI unit, but every SI unit MUST have a unitType from which a mapping could be devised. In many cases unitTypes have well-used terms (e.g. "mass", "velocity") but some unitTypes arise from combination of simpler concepts and do not have well defined terms. Examples occur in high powers of dimensions (e.g. in Virial coefficients or high order rate constants). In these cases there is no meaningful natural language term and we use a combination of dimensions (e.g. "ML-5T-5". The reason for including these in dictionaries is to force the inclusion of units in documents and dictionaries. Some unitTypes may have the same dimensions but represent different mathematical quantities. Thus energy and torque both have dimension ML2T-2 but represent the scalar (dot) and vector (cross) products respectively. Some units are formed by ratios or multiplication. Thus energy-per-mass (various "specific heats") have the units ML2T-2.M-1 => L2T-2 , i.e. velocity-squared. However we may provide separate entries for these, while we do not provide different forms of energy. unitType MUST not be used to define quantities or other concepts. Thus entropy and specific heat have the same unitType but may be thought of as separate quantities. Heat and work (free energy) are similar. unitType provides dimensions and this can be used for dimensional analysis and unit conversion. THIS DICTIONARY IS NOT COMPLETE or validated. There may be duplicate entries and some may be wrong. PLEASE CONTRIBUTE TO THIS DICTIONARY, e.g. by transcribing or linking to Wikipedia, and adding your own comments An unreported unit Used when a document has failed to provide units but where it is clear that there should be some sort of units. It is sometimes very difficult to work out the units, but unknown should not be used as an excuse for not trying. By contrast none means that the concept does not carry units. Cannot be used in units algebra. Peter Murray-Rust A quantity without an associated physical dimension This is a difficult concept and users should read the Wikipedia article and further references. dimensionless can be used for numeric quantities which formally have no units such as dimensionless constants. It can also be used for ratios of quantities with units (e.g. mg/kg). Cancelling units loses semantic information and we shall try in CML to avoid this if possible. dimensionless MUST not be used for concepts which are not numeric (e.g. algorithms) or pure numbers and none SHOULD be used. Dimensionless in Wikipedia Peter Murray-Rust Wikipedia A term signifying that the concept cannot carry units. Use for dictionary concepts that cannot carry units. These include methods, names of programs, authors. none MUST not be used for concepts which should carry units or which can be formally classified as dimensionless. See also dimensionless. Peter Murray-Rust Mass used as a type of unit corresponding to dimension M . Mass is a difficult concept. In Chemistry the three types of mass (inertial mass, active gravitational mass, and passive gravitational mass) are generally used interchangeably. Here mass is used as the type of the unit and can be linked to the fundamental M dimension. Mass should never be used as a synonym for weight. see Mass in Wikipedia Peter Murray-Rust TODO TODO Wikipedia Length is a measure of one dimension Length is a measure of one dimension, whereas area is a measure of two dimensions (length squared) and volume is a measure of three dimensions (length cubed). In most systems of measurement, the unit of length is a fundamental unit, from which other units are defined. In the physical sciences and engineering, when one speaks of "units of length", the word "length" is synonymous with "distance". The metre (or meter), symbol m, is the base unit of length in the International System of Units (SI). Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole (at sea level), its definition has been periodically refined to reflect growing knowledge of metrology. Since 1983, it is defined as the length of the path travelled by light in vacuum in 1⁄299,792,458 of a second. TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO the rate at which work is performed or energy is converted TODO - http://en.wikipedia.org/wiki/Power TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO decay per unit time TODO TODO L2T-2 TODO Amount per time T-1A TODO moles of substance per volume of solution TODO moles of substance per mass of solution TODO area or squared length TODO Volume or cubic length TODO Reciprocal volume. TODO Length power -4. TODO Rate of change of length or position TODO The radioactive equivalent dose is found by multiplying the radioactive absorbed dose by a dimensionless "quality factor" Q dependent of radiation type and by another dimensionless number, N, dependent on all other pertinent factors The radioactive equivalent dose has the same dimensions as the gray ( i.e. joules per kilogram - or m2s-2), it measures a different quantity. To avoid confusion between the absorbed dose and the equivalent dose, the corresponding special units, namely the gray for absorbed dose and the sievert for the dose equivalent, are used. For a given amount of radiation (measured in gray - the plural of gray is gray), the biological effect (measured in sievert) can vary considerably as a result of the radiation weighting factor WR. This variation in effect is attributed to the Linear Energy Transfer [LET] of the type of radiation, creating a different relative biological effectiveness for each type of radiation under consideration. Per most government regulations, the RBE [Q] for electron and photon radiation is 1, and varies for other types of radiation Rate of change of velocity TODO Rate of change of angle TODO mass times velocity TODO mass times angular velocity TODO - is this right? cross product of length and force TODO Reciprocal length or inverse length is often used in spectroscopy as a measure of energy but in other areas it could be the absorption coefficient or attenuation coefficient in materials science or the curvature of a line in mathematics. Reciprocal length or inverse length is a measurement used in several branches of science and mathematics. As the reciprocal of length, common units used for this measurement include the reciprocal metre or inverse metre (m−1), the reciprocal centimetre or inverse centimetre (cm−1), and, in optics, the dioptre. mass per unit volume TODO Volume per unit mass TODO Amount per unit volume TODO Volume per mole TODO Energy per unit temperature TODO Energy per mole per unit temperature change or molar Entropy TODO Heat capacity or entropy per unit mass TODO Energy or work per mole TODO Force per mole Molar force is a unit type often used as an abort criterion in minmization procedures. In those cases it defines the maximal force per mole that is allowed to accept a certain configuration as final. Energy or work per unit mass TODO Energy or work per unit volume TODO Energy per unit area or force per unit length Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent—but when referring to energy per unit of area, people use the term surface energy—which is a more general term in the sense that it applies also to solids and not just liquids. TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO Charge per unit volume TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO Luminous intensity per area TODO TODO TODO TODO TODO Gradient of energy with respect to length. TODO TODO TODO TODO Amount per unit volume TODO Reciprocal molar mass TODO TODO TODO Rate of change of angular velocity TODO Reciprocal area TODO area per unit mass TODO Mass per unit area TODO Rate of change of areal mass density TODO Rate of change of areal mass density TODO TODO TODO TODO TODO TODO TODO TODO TODO Current per unit area TODO TODO TODO TODO TODO TODO TODO The electric dipole moment vector. The electric dipole moment is a measure of the separation of positive and negative electrical charges in a system of charges, that is, a measure of the charge system's overall polarity. wikipedia article TODO TODO TODO TODO TODO TODO A measure of how strongly a material opposes the flow of electric current. Electrical resistivity (also known as resistivity, specific electrical resistance, or volume resistivity) is a measure of how strongly a material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. Resistivity is commonly represented by the Greek letter ρ (rho). Electrical resistivity in Wikipedia Wikipedia TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO TODO ML-2T-1 TODO TODO TODO Rate of change of mass MT-1 TODO Hannah Barjat Rate of change of in molar concentration with time. This unit type may be used in the measurement of a change of molar concentration, due to physical or chemical process over time. Hannah Barjat Inverse of molar concentration per second. These are the units of a second order rate coefficient. Hannah Barjat Inverse of molar concentration squared per second. These are the units of a third order rate coefficient. mass per mass TODO TODO ML-1 TODO TODO MA-1 TODO TODO ML2 TODO TODO wrong? TODO TODO wrong? TODO TODO wrong? TODO Disintegrations per second TODO TODO TODO Charge per unit area TODO TODO TODO volume per unit area L3L-2 TODO Reciprocal volume L-3 TODO Rate of change of volume L3T-1 TODO