The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
dek-
DEFINITION:
To take, accept. Oldest form *de-, becoming *dek- in centum languages. Derivatives include decent, paradox, and disdain. 1. Suffixed (stative) form *dek--.decent, from Latin decre, to be fitting (< “to be acceptable”). 2. Suffixed (causative) o-grade form *dok-eye-.a.docent, docile, doctor, doctrine, document, from Latin docre, to teach (< “to cause to accept”); b.dogma, dogmatic; Docetism, doxology, heterodox, orthodox, paradox, from Greek dokein, to appear, seem, think (< “to cause to accept or be accepted”). 3. Suffixed form *dek-es-.a.décor, decorate, from Latin decus, grace, ornament; b.decorous, from Latin decor, seemliness, elegance, beauty. 4. Suffixed form *dek-no-.dainty, deign, dignity; condign, dignify, disdain, indign, indignant, indignation, from Latin dignus, worthy, deserving, fitting. 5. Reduplicated form *di-dk-ske-.disciple, discipline, from Latin discere, to learn. 6.dowel, pandect, synecdoche, from Greek dekhesthai, to accept. 7. Suffixed o-grade form *dok-o-.diplodocus, from Greek dokos, beam, support. (Pokorny 1. de- 189.)
-, becoming *dek- in centum languages. 
-. decent, from Latin dec
