The cardinal number equal to nine plus one, representing the base unit of the decimal counting system inherited from Proto-Indo-European *déḱm̥.
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Proto-Indo-Europeanc. 4500–2500 BCEwell-attested
The number ten is one of the most perfectly preserved words in the entire Indo-European family — a direct inheritance from PIE *déḱm̥, which linguists recover with unusual confidence because every major branch preserves it. The form appears in Sanskrit as dáśa, Avestan as dasa, Greek as déka, Latin as decem, Gothic as taihun, OldEnglish as tīen, Welsh as deg, Old Irish as deich, Lithuanian as dešimt, Russian as desyat', and Armenian as tasn. The root almost certainly reflects the anatomical reality of
, and PIE *déḱm̥ may be cognate with *deḱ- meaning 'right hand' or 'to take/grasp', suggesting the original numeral was conceptually 'two hands' or 'the whole count'. Latin decem
Old French disme from Latin decima (a tenth). The Germanic branch shifted the initial consonant by Grimm's Law: PIE *d- became Germanic *t-, producing Old English tīen → Modern English ten, and German zehn. Key roots: *déḱm̥ (Proto-Indo-European: "ten; the complete finger-count; possibly 'two hands'"), *deḱ- (Proto-Indo-European: "to take / right hand; possibly the anatomical basis for the numeral (→ Latin dexter 'right')"), decem (Latin: "ten — source of decimal, decimate, December, dean, dime, dozen"), déka (δέκα) (Ancient Greek: "ten — source of deca- prefix in decade, decathlon, decagon").
decem(Latin (true cognate from PIE *déḱm̥))déka (δέκα)(Ancient Greek (true cognate from PIE *déḱm̥))dáśa(Sanskrit (true cognate from PIE *déḱm̥))desyat' (десять)(Russian (true cognate from PIE *déḱm̥))dešimt(Lithuanian (true cognate from PIE *déḱm̥))zehn(German (true cognate from PIE *déḱm̥ via Grimm's Law))