déḱm̥

The PIE numeral for "ten," reconstructed as *déḱm̥, is fundamental to the centum–satem classification.‌​‍​‍​‌​‍​‌​‌​‌​‍​‌​‌​‍​‌​‍​‌​‍​‍​‍​‍​‍​‍​‌​‌​‌​‌​‍​‍​‌​‌​‌​‍​‌ Regular reflexes include Latin decem, Greek déka, Sanskrit dáśa, Gothic taihun, and Lithuanian dẽšimt.

Discussion

The numeral *déḱm̥ ("ten") occupies a central position in PIE reconstruction both for its phonologic‌​‍​‍​‌​‍​‌​‌​‌​‍​‌​‌​‍​‌​‍​‌​‍​‍​‍​‍​‍​‍​‌​‌​‌​‌​‍​‍​‌​‌​‌​‍​‌al regularity and for its historical role in establishing the centum–satem classification of the Indo-European languages. The treatment of the palatal stop *ḱ in this word — retained as a velar in the centum languages and shifted to a sibilant or affricate in the satem languages — provided the nineteenth-century diagnostic for this division, first articulated by von Bradke (1890). The reconstruction is given in Pokorny (IEW 191), Szemerényi (1996), and Sihler (New Comparative Grammar of Greek and Latin, 1995).

Latin decem shows the centum treatment: *ḱ > c (velar). The ordinal decimus and the derived forms decimāre ("to take a tenth"), decuria ("group of ten"), and the calendar term December ("tenth month" in the early Roman calendar) are all transparent continuations. Greek déka (δέκα), with the same centum reflex, contributed the prefix deka- to modern scientific nomenclature (decagon, decathlon, decade). The Italic and Greek forms agree in showing the regular outcome of *ḱ as a plain velar.

Sanskrit dáśa demonstrates the satem shift *ḱ > ś with full regularity. Avestan dasa and Old Persian *daθa (inferred from derivative forms) confirm the Indo-Iranian development. In the Balto-Slavic branch, Lithuanian dẽšimt and Old Church Slavonic desętĭ likewise show the expected sibilant reflex of the palatal. The contrast between Latin decem and Sanskrit dáśa — c versus ś from the same proto-phoneme — was among the earliest and most compelling demonstrations of regular sound correspondence in the history of comparative linguistics.

In Germanic, Gothic taihun and Old English tīen (Modern English ten) show the application of Grimm's Law: *d > t and *ḱ (merged with *k in pre-Germanic) > *h (> h in Gothic, lost in later Germanic). German zehn and Dutch tien continue Proto-Germanic *tehun. Old Irish deich and Welsh deg preserve the Celtic reflex. Tocharian B śak shows the independent satem-like treatment characteristic of Tocharian, complicating the simple centum–satem binary.

The PIE decimal system, evidenced by the reconstructability of cardinal numerals from "one" (*Hóynos) through "ten" (*déḱm̥) and the compound "hundred" (*ḱm̥tóm, from *dḱm̥tóm, "a set of tens"), points to a base-ten counting system. Szemerényi (1960) proposed an etymological connection between *déḱm̥ and *deḱ- interpreted as "two hands" (i.e., two sets of five fingers), a hypothesis that remains speculative but has not been refuted. The numeral continues to serve as a primary test case for sound-law regularity in introductory Indo-European coursework.

Laryngeal Analysis

No laryngeal.

Ablaut

Invariable numeral with zero-grade root.