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The international system of units consists of a set of units together with a set of prefixes. The units of SI can be divided into two subsets. There are the seven base units. Each of these base units are nominally dimensionally independent. From these seven base units several other units are derived. In addition to the SI units there are also a set of non-SI units accepted for use with SI.SI base units NameSymbolQuantitymetremlengthkilogramkgmasssecondstimeampereAelectric currentkelvinKthermodynamic temperaturemolemolamount of substancecandelacdluminous intensityA prefix may be added to units to produce a multiple of the original unit. All multiples are integer powers of ten. For example, kilo- denotes a multiple of a thousand and milli- denotes a multiple of a thousandth hence there are one thousand millimetres to the metre and one thousand metres to the kilometre. The prefixes are never combined: a millionth of a kilogram is a milligram not a microkilogram.SI Prefixes Nameyotta-zetta-exa-peta-tera-giga-mega-kilo-hecto-deca-SymbolYZEPTGMkhdaFactor10^{24}10^{21}10^{18}10^{15}10^{12}10^{9}10^{6}10^{3}10^{2}10^{1}Namedeci-centi-milli-micro-nano-pico-femto-atto-zepto-yocto-SymboldcmµnpfazyFactor10^{-1}10^{-2}10^{-3}10^{-6}10^{-9}10^{-12}10^{-15}10^{-18}10^{-21}10^{-24}

This does not answer my question of why nanometer are the preferred measurement?

It's not just engineers and such who use powers of 10 that are multiples of 3, most English speakers do to. Thousands, millions and billions all have words for them in English in a way that 10000 (for example) doesn't.A nanometre is a billionth of a metre; 10^-10 of a metre would be a hundred thrillionths of a metre or a tenth of a billionth of a metre. I don't see that as a particularly logical choice.

... but for counting years we use(d) centuries rather than millennia (millenniums ?) e.g. 1985 was read nineteen (hundred) eightyfive rather than onethousand ninehundred eightyfive.