digitus

Traditionally derived from Proto-Italic *digitos, from Proto-Indo-European *deyǵ- (“to show, point out, pronounce solemnly”), variant of the root *deyḱ- that also gave Latin dīcō (“I say, speak talk”) and English toe (though De Vaan is skeptical due to the presumed phonetic processes resulting in the change of a ḱ- to a ǵ- having no other examples in Latin).^[1] Fingers were thus "pointers, indicators". The "digit" sense comes from the fact that they were used for counting up to ten.

Indo-European cognates include Sanskrit दिशति (diśáti, “to show, point out”), Ancient Greek δείκνυμι (deíknumi, “to show”), δίκη (díkē, “manner, custom”), Old English tǣċan (“to show, point out”)(English teach) and tācen (English token).

Compare similar semantic shift in English in the cognate word teacher (“forefinger, index finger”).

Pronunciation

(Classical) IPA^(key): /ˈdi.ɡi.tus/, [ˈd̪ɪɡɪt̪ʊs̠]
(modern Italianate Ecclesiastical) IPA^(key): /ˈdi.d͡ʒi.tus/, [ˈd̪iːd͡ʒit̪us]

Noun

digitus m (genitive digitī); second declension

a finger, toe
(mathematics) a digit
an inch (in ancient times, a 16th part of a Roman foot)
a twig

Declension

Second-declension noun.

Case	Singular	Plural
Nominative	digitus	digitī
Genitive	digitī	digitōrum
Dative	digitō	digitīs
Accusative	digitum	digitōs
Ablative	digitō	digitīs
Vocative	digite	digitī

Note: the genitive plural digitum is attested in Vitruvius and in a fragment of Varro (quoted by the grammarian Charisius).

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