Basic and Helpful Symbols  Weights  Measures You Might Want To Know
Greek Letters
Units of Length
Meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.
Kilometer is a unit of length in the metric system, equal to one thousand meters.  One (1) km = 1,000 m or 100,000 cm  One (1) km = 0.621 statute miles Centimeter is a unit of length in the metric system, equal to one hundredth of a meter.  One (1) cm = 10 mm or 1 m/100 Millimeter is a unit of length in the metric system, equivalent to one thousandth of a meter.  One (1) mm = 1,000 micrometres  One (1) mm = 1,000,000 nanometers  There are 25.4 mm in one inch. Micrometer is an SI derived unit of length equaling onemillionth of a metre (or onethousandth of a millimetre, 0.001 mm, or about 0.000039 inches). The symbol µm is sometimes rendered as um if the symbol µ cannot be used. The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of cells and bacteria.  One (1) μm = 0.001 mm  One (1) μm = 0.000039 inches Nanometre is a unit of length in the metric system, equal to one billionth of a meter.  One (1) nm = 1 m / 1,000,000,000 Concentration is the abundance of a constituent divided by the total volume of a mixture. To concentrate a solution, one must add more solute or reduce the amount of solvent. By contrast, to dilute a solution, one must add more solvent, or reduce the amount of solute.
Units of Concentration
Conversion Factors

Units of Heat
cal: small calorie or gram calorie/approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius. In scientific context, the term calorie almost always refers to the small calorie.
kal or Cal: large calorie/kilocalorie/kilogram calorie/dietary calorie/nutritionist's calorie/food calorie — equal to 1000 small calories (cal). In nutritional context "calorie" and "kilocalorie" mean the same thing. In the CGS system (The Centimetregramsecond System), heat is measured in calories. In the SI system (International System of Units), heat energy is measured in joules (J). One calorie = 4.185 joules. Base SI* Units*SI system (International System of Units)
Meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.
Kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram. Mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is "mol." When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles. Second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. Kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. Ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular crosssection, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 107 newton per meter of length. Candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. Katal is the SI unit of catalytic activity — unit for expressing quantity values of catalytic activity of enzymes and other catalysts. What does Volume measure? The threedimensional space a substance (solid/liquid/gas/plasma) contains, using the the cubic meter. The volume of a container, for example, is the amount of fluid (gas/liquid) that the container could hold, not the amount of space the container displaces.
Units of Volume
Liter or litre is a unit of volume equal to 1/1,000 cubic metre or 1 cubic decimetre.
Deciliter is a common metric unit of volume — equal to 0.1 liter or 100 cubic centimeters. Milliliter is a common metric unit of volume — equal to 0.001 liter, exactly one cubic centimeter. Microliter is a metric unit of volume used in chemistry and medicine to measure very small quantities of liquid — equal to 0.001 milliliter or 1 cubic millimeter. It is also called lambda. 
Metre is used as the
standard spelling of the metric unit for length in all Englishspeaking nations except the USA, which uses meter. CGS or cgs is The Centimetregramsecond system — a metric system of physical units based on centimetre as the unit of length, gram as a unit of mass, and second as a unit of time. All CGS mechanical units are derived from these three base units. The CGS system has been largely supplanted by the MKS system, based on metre, kilogram, and second. MKS was in turn replaced by the International System of Units (SI). The latter adopts the three base units of MKS, plus the ampere, mole, candela and kelvin. In many fields of science and engineering, SI is the only system of units in use.
