kar- / Indo-European roots
Examples of words with the root kar-: -ard, -cracy, canker, carcino-, carcinoma, careen, carina, chancre, craton, eukaryote, gillyflower, hard, hardy, karyo-, standard, synkaryon.
▲ Derivatives include hard, cancer.
I. Variant form *ker-.
1. Suffixed o-grade form *kor-tu-. a. hard, hardly from Old English hard, heard, hard; b. -ard from Germanic *-hart, *-hard, bold, hardy; c. standard from Old French estandard, flag marking a rallying place in battle, from Frankish *hard, hard; d. hardy1 from Old French hardir, to make hard. a-d all from Germanic *harduz.
2. Suffixed zero-grade form *kr̥t-es-, from earlier full-grade form *kret-es-. -cracy from Greek kratos, strength, might, power.
II. Possible basic form *kar- in derivatives referring to things with hard shells.
1. Possibly Latin carīna, keel of a ship, nutshell careen, carina
2. Possibly Greek karuon, nut karyo-; eucaryote, gillyflower, synkaryon
3. Reduplicated form *kar-kr-o-. cancer, canker, carangid, chancre from dissimilated Latin cancer, crab, cancer, constellation Cancer.
4. Suffixed form *kar-k-ino-. carcino-, carcinoma from Greek karkinos, cancer, crab.
[Pokorny 3. kar- 531.]