英和和英

語源

Blend of r (an arbitrarily chosen initial letter) +‎ Ancient Greek ἐννέα (ennéa, “nine”) +‎ -a (to match the final letter of the SI prefixes from mega- upwards).

Coined by Richard J. C. Brown and adopted by the General Conference on Weights and Measures in 2022 as an expansion to the metric prefixes beyond 10.

Some popular unofficial terms already in use were hella-, bronto- and xenna-, but terms beginning with the same letters as existing prefixes were considered undesirable, as were as those beginning with common scientific letters such as b or x. Richard J. C. Brown suggested that the new terms begin with r and q, due to their rarity as unit symbols, and that the trends followed by the other prefixes be continued: that they be based on Latin or Greek; that large prefixes end with -a and small prefixes end with -o; that they should be in corresponding large and small pairs; and that the first letters of each prefix should be in reverse alphabetical order (as has been the case for the newer prefixes). He therefore suggested ronna- and ronto- (evoking Ancient Greek ἐννέα (ennéa) and Latin novem (“nine”)), and quecca- and quecto- (evoking Ancient Greek δέκα (déka) and Latin decem (“ten”)), because as 10 and 10 when written have nine and ten groups of zeroes, respectively. These were adopted, with quecca- changed to quetta-.