context is unclear). This informal postfix is read or spoken as "thousand" or "grand", or just "k". The financial and general news media mostly use m or M, b or B, and t or T as abbreviations for million, billion (109) and trillion (1012), respectively, for large quantities, typically currency and population. The medical and automotive fields in the United States use the abbreviations cc or ccm for cubic centimetres. One cubic centimetre is equal to one millilitre. For nearly a century, engineers used the abbreviation MCM to designate a "thousand circular mils" in specifying the cross-sectional area of large electrical cables. Since the mid-1990s, kcmil has been adopted as the official designation of a thousand circular mils, but the designation MCM still remains in wide use. A similar system is used in natural gas sales in the United States: m (or M) for thousands and mm (or MM) for millions of British thermal units or therms, and in the oil industry, where MMbbl is the symbol for "millions of barrels". This usage of the capital letter M for "thousand" is from Roman numerals, in which M means 1000. Binary prefixes The original metric system adopted by France in 1795 included the two binary prefixes double- (2×) and demi- (×). However, they were not retained when the SI prefixes were internationally adopted by the 11th CGPM conference in 1960. In some fields of information technology, it has been common to designate non-decimal multiples based on powers of 1024, rather than 1000, for some SI prefixes (kilo-, mega-, giga-), contrary to the definitions in the International System of Units (SI). The SI does not permit the metric prefixes to be used in this conflicting sense. This practice was once sanctioned by some industry associations, including JEDEC. The International Electrotechnical Commission (IEC) standardised the system of binary prefixes (kibi-, mebi-, gibi-, etc.) for this purpose. See also Binary prefix Engineering notation E1 series (preferred numbers) Indian numbering system International vocabulary of metrology ISO/IEC 80000 Names of large numbers Names of small numbers Number names Numeral prefix Order of magnitude Orders of magnitude (data) RKM code SI base unit Unified Code for Units of Measure Footnotes References External links International Bureau of Weights and Measures (BIPM) SI prefixes at BIPM US NIST Definitions of the SI units: The twenty SI prefixes US NIST Definitions of the SI units: The binary prefixes Numeral systems