Meaning of ATTO- in English

ATTO-

/ ˈætəʊ; NAmE ˈætoʊ/ combining form

(in units of measurement) a factor of 10 -18 :

200 attowatts

••

WORD ORIGIN

from Danish or Norwegian atten eighteen.

Oxford Advanced Learner's English Dictionary.      Оксфордский английский словарь для изучающик язык на продвинутом уровне.