Tera is a unit prefix in the metric system denoting multiplication by one trillion, or 1012 or 1000000000000 (one trillion short scale; one billion long scale). It has the symbol T. Tera is derived from the Greek word τέρας teras, meaning "monster";[1] also it resembles tetra, meaning "four" but with the middle letter removed as it is the fourth power of 1000.[2] The unit prefix was confirmed for use in the International System of Units (SI) in 1960.

Examples of its use:

Prefix Base 10 Decimal English word Adoption[nb 1] Etymology
Name Symbol Short scale Long scale Language Derived word
yotta Y 1024 1000000000000000000000000 septillion quadrillion 1991 Greek eight[nb 2]
zetta Z 1021 1000000000000000000000 sextillion trilliard 1991 Latin seven[nb 2]
exa E 1018 1000000000000000000 quintillion trillion 1975 Greek six
peta P 1015 1000000000000000 quadrillion billiard 1975 Greek five[nb 2]
tera T 1012 1000000000000 trillion billion 1960 Greek four,[nb 2] monster
giga G 109 1000000000 billion milliard 1960 Greek giant
mega M 106 1000000 million 1873 Greek great
kilo k 103 1000 thousand 1795 Greek thousand
hecto h 102 100 hundred 1795 Greek hundred
deca da 101 10 ten 1795 Greek ten
100 1 one
deci d 10−1 0.1 tenth 1795 Latin ten
centi c 10−2 0.01 hundredth 1795 Latin hundred
milli m 10−3 0.001 thousandth 1795 Latin thousand
micro μ 10−6 0.000001 millionth 1873 Greek small
nano n 10−9 0.000000001 billionth milliardth 1960 Greek dwarf
pico p 10−12 0.000000000001 trillionth billionth 1960 Spanish peak
femto f 10−15 0.000000000000001 quadrillionth billiardth 1964 Danish fifteen, Fermi[nb 3]
atto a 10−18 0.000000000000000001 quintillionth trillionth 1964 Danish eighteen
zepto z 10−21 0.000000000000000000001 sextillionth trilliardth 1991 Latin seven[nb 2]
yocto y 10−24 0.000000000000000000000001 septillionth quadrillionth 1991 Greek eight[nb 2]
  1. ^ Prefixes adopted before 1960 already existed before SI. The introduction of the CGS system was in 1873.
  2. ^ a b c d e f Part of the beginning of the prefix was modified from the word it was derived from, ex: "peta" (prefix) vs "penta" (derived word).
  3. ^ The fermi was introduced earlier with the same symbol "fm", in which then the "f" became a prefix. The Danish word is used since it is vaguely spelled similar to fermi.

See alsoEdit

ReferencesEdit

  1. ^ "SI prefixes and their etymologies". US Metric Association. Retrieved 2021-06-11.
  2. ^ C. Upward, G. Davidson, The History of English Spelling, Wiley-Blackwell (2011)