deik- / Indo-European roots
Examples of words with the root deik-: abdicate, addict, apodictic, benediction, betoken, condition, contradict, dedicate, deictic, deixis, dicast, dictate, diction, dictum, dictyosome, digit, disk, ditto, ditty, edict, fatidic, index, indicate, indiction, indite, interdict, judge, judicial, juridical, jurisdiction.
To show, pronounce solemnly; also in derivatives referring to the directing of words or objects.Oldest form *deik̑-, becoming *deik- in centum languages.
▲ Derivatives include teach, toe, addict, preach, judge, revenge, disk.
I. Variant *deig-.
1. O-grade form *doig-. a. teach from Old English tǣcan, to show, instruct, from Germanic *taikjan, to show; b. (i) token from Old English tācen, tācn, sign, mark; (ii) betoken from Old English tācnian, to signify; (iii) tetchy from Gothic taikns, sign; (iv) tachisme from Old French tache, teche, mark, stain. (i)-(iv) all from Germanic *taiknam..
2. Zero-grade form *dig-. digit from Latin digitus, finger (< "pointer" "indicator").
II. Basic form *deik-.
1. Possibly o-grade form *doik-. toe from Old English tā, tahe, toe, from Germanic *taihwō.
2. Basic form *deik-. dictate, diction, dictum, ditto, ditty; addict, benediction, condition, contradict, edict, fatidic, herb bennet, indict, indiction, indite, interdict, juridical, jurisdiction, maledict, malison, predict, valediction, verdict, veridical, voir dire from Latin dīcere, to say, tell.
3. Suffixed zero-grade form *dik-ā-. abdicate, dedicate, preach, predicament, predicate from Latin dicāre, to proclaim.
4. Agential suffix *-dik-. a. index, indicate from Latin index, indicator, forefinger (in-, toward; see en); b. judge, judicial; prejudice from Latin iūdex (< *yewes-dik-), judge, "one who shows or pronounces the law" (iūs, law; see yewes-); c. vendetta, vindicate; avenge, revenge from Latin vindex (first element obscure), surety, claimant, avenger.
5. deictic, deixis; apodictic, paradigm, policy2 from Greek deiknunai, to show, and noun deigma (*deik-mn̥), sample, pattern.
6. Zero-grade form *dik-. disk; dictyosome from suffixed form *dik-skos, from Greek dikein, to throw (< "to direct an object").
7. Form *dikā-. dicast; syndic, theodicy from Greek dikē, justice, right, court case.
[Pokorny deik̑- 188.]