The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
dek
DEFINITION:
Ten. Oldest form *de, becoming *dek in centum languages. Derivatives include ten, December, decimate, dean, hundred, century, and hecatomb. I. Basic form *dek.1a.ten, from Old English ten, ten; b. Old Norse tjan, ten, in compound ttjn (see okt(u)). Both a and b from Germanic *tehun.2.eighteen, fifteen, fourteen, nineteen, seventeen, sixteen, thirteen, from Old English suffix -tne,-tne,-tne, ten, -teen, from Germanic *tehan.3. deci-, decimal, decimate, decuple, decurion, dicker, dime; December, decemvir, decennary, decennium, decussate, dozen, duodecimal, octodecimo, sextodecimo, from Latin decem, ten. 4.denarius, denary, denier2, dinar, from irregular Latin distributive dn, by tens, ten each (formed by analogy with nn, nine each). 5.dean, deca-, decade, doyen; decagon, Decalogue, dodecagon, from Greek deka, ten. II. Germanic *tigu-, ten, decad (of uncertain formation, as though < *deku-), in compound *twgentig (see dwo-). III. Ordinal number *dekto-.tenth, tithe, from Old English teogotha,totha, tenth, from Germanic *teguntha-. IV. Suffixed zero-grade form *-dk-t, reduced to *-kt, and lengthened o-grade form *-dkm-t, reduced to *-kont.1.nonagenarian, octogenarian, Septuagint, sexagenary, from Latin -gint, ten times. 2.Pentecost, from Greek *-konta, ten times. V. Suffixed zero-grade form *dk-tom, hundred, reduced to *ktom.1.hundred, from Old English hundred, from dialectal North and West Germanic *hund(a)-rada- (-rada-, from Germanic *radam, number; see ar-), from Germanic *hundam, hundred. 2. Germanic compound *ths-hundi, swollen hundred, thousand (see teu-). 3.cent, cental, centas, centavo, centenarian, centenary, centesimal, centi-, centime, centner, centum, century, qindarka; centennial, cinquecento, percent, quattrocento, seicento, sen2, seniti, sexcentenary, trecento, from Latin centum, hundred. 4.hecatomb, hecto-, from Greek hekaton, a hundred (? dissimilated from *hem-katon, one hundred; *hem-, one; see sem-1). 5.stotinka, from Old Church Slavonic sto, hundred. 6.satem, from Avestan satm, hundred. (Pokorny de 191.) See also compound root wkt.