YOCTO- Meaning of YOCTO- in English [ 'jɒktəʊ ]■ combining form denoting a factor of 10 -24 : yoctojoule. Originadapted from octo- , on the pattern of combining forms such as peta- and exa- . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004