atto-

prefix

In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10⁻¹⁸ (short scale quintillionth or long scale trillionth).

Opposite
exa-
OriginDanish atten →
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Meanings

prefix
  1. In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10⁻¹⁸ (short scale quintillionth or long scale trillionth).

Synonyms & antonyms

Opposite
exa-

Origin

  1. Danishatten“eighteen”
  2. Englishatto-

From Danish atten (“eighteen”), with reference to the (negative) exponent in the relevant power of ten; the same principle also explains femto-.

More words from Danish

Full word history & related roots →

Translations

Bulgarian ато-
  • ато- (ato-)unit of measure
Catalan atto-
  • atto-unit of measure
Chinese Mandarin 阿托
  • 阿托 (ātuō)unit of measure
Danish atto-
  • atto-unit of measure
Dutch atto-
  • atto-unit of measure
Finnish atto-
  • atto-unit of measure
French atto-
  • atto-unit of measure
German atto-
  • atto-unit of measure
Hungarian atto-
  • atto-unit of measure
Icelandic attó-
  • attó-unit of measure
Indonesian ato-
  • ato-unit of measure
Irish ata-
  • ata-unit of measure
Japanese アト-
  • アト- (ato-)unit of measure
Korean 아토-
  • 아토- (ato-)unit of measure
Malay ato-
  • ato-unit of measure
Polish atto-
  • atto-unit of measure
Russian атто-
  • атто- (atto-)unit of measure
Spanish atto-
  • atto-unit of measure
Thai อัตโต-
  • อัตโต- (at-too-)unit of measure
Ukrainian атто-
  • атто- (atto-)unit of measure
Vietnamese a-tô
  • a-tôunit of measure
Cite this entry
APA

atto-. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/atto-

MLA

“atto-.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/atto-. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “atto-,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/atto-.

Source: atto- on Wiktionary, CC BY-SA 4.0.