combining form Etymology: International Scientific Vocabulary, from Danish or Norwegian atten eighteen, from Old Norse āttjān; akin to Old English eahtatīene eighteen one quintillionth (10 -18 ) part of
ATTO-
Meaning of ATTO- in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012