Proto-Indo-European root meaning "to call, shout."

It forms all or part of: call; clatter; Gallic; gallinaceous; gallium; glasnost; Glagolitic.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit garhati "bewail, criticize;" Latin gallus "cock;" Old English ceallian "to shout, utter in a loud voice," Old Norse kalla "to cry loudly," Dutch kallen "to talk, chatter;" German Klage "complaint, grievance, lament, accusation;" Old English clacu "affront;" Old Church Slavonic glasu "voice," glagolu "word;" Welsh galw "call."

also *g(a)lakt-, Proto-Indo-European root meaning "milk."

It forms all or part of: ablactation; cafe au lait; galactic; galaxy; lactate (v.); lactate (n.); lactation; lacteal; lactescence; lactic; lactivorous; lacto-; lactose; latte; lettuce.

It is the hypothetical source of/evidence for its existence is provided by: Latin lac (genitive lactis) "milk;" Greek gala (genitive galaktos), "milk;" Armenian dialectal kaxc' "milk." The initial "g" probably was lost in Latin by dissimilation. This and the separate root *melg-, account for words for "milk" in most of the Indo-European languages. The absence of a common word for it is considered a mystery.

Proto-Indo-European root meaning "cold; to freeze." 

It forms all or part of: chill; cold; congeal; cool; gel; gelatine; gelatinous; gelato; gelid; glace; glacial; glaciate; glaciation; glacier; glaciology; glacis; jell; jelly.

It is the hypothetical source of/evidence for its existence is provided by: Latin gelare "to freeze," gelu "frost," glacies "ice;" Old English cald "cold, cool," German kalt.

Proto-Indo-European root meaning "tooth, nail." 

It forms all or part of: cam (n.1) "projecting part of a rotating machinery;" comb; gem; oakum; unkempt.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit jambha-s "tooth;" Greek gomphos "peg, bolt, nail; a molar tooth;" Albanian dhemb "tooth;" Old English camb "comb." 

*genə-, also *gen-, Proto-Indo-European root meaning "give birth, beget," with derivatives referring to procreation and familial and tribal groups.

It forms all or part of: Antigone; autogenous; benign; cognate; congener; congenial; congenital; connate; cosmogony; cryogenic; degenerate; engender; engine; epigone; eugenics; -gen; gendarme; gender; gene; genealogy; general; generate; generation; generic; generous; genesis; -genesis; genial; -genic; genital; genitive; genius; genocide; genotype; genre; gens; gent; genteel; gentile; gentle; gentry; genuine; genus; -geny; germ; german (adj.) "of the same parents or grandparents;" germane; germinal; germinate; germination; gingerly; gonad; gono-; gonorrhea; heterogeneous; homogeneous; homogenize; homogenous; impregnate; indigenous; ingenious; ingenuous; innate; jaunty; kermes; kin; kindergarten; kindred; king; kind (n.) "class, sort, variety;" kind (adj.) "friendly, deliberately doing good to others;" Kriss Kringle; malign; miscegenation; nada; naive; nascent; natal; Natalie; nation; native; nature; nee; neonate; Noel; oncogene; ontogeny; photogenic; phylogeny; pregnant (adj.1) "with child;" primogenitor; primogeniture; progenitor; progeny; puisne; puny; renaissance; theogony; wunderkind.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit janati "begets, bears," janah "offspring, child, person," janman- "birth, origin," jatah "born;" Avestan zizanenti "they bear;" Greek gignesthai "to become, happen," genos "race, kind," gonos "birth, offspring, stock;" Latin gignere "to beget," gnasci "to be born," genus (genitive generis) "race, stock, kind; family, birth, descent, origin," genius "procreative divinity, inborn tutelary spirit, innate quality," ingenium "inborn character," possibly germen "shoot, bud, embryo, germ;" Lithuanian gentis "kinsmen;" Gothic kuni "race;" Old English cennan "beget, create," gecynd "kind, nature, race;" Old High German kind "child;" Old Irish ro-genar "I was born;" Welsh geni "to be born;" Armenian cnanim "I bear, I am born."

Proto-Indo-European root meaning "knee; angle."

It forms all or part of: agonic; decagon; diagonal; geniculate; genuflect; genuflection; -gon; goniometer; heptagon; hexagon; knee; kneel; octagon; orthogonal; pentagon; polygon; trigonometry.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit janu, Avestan znum, Hittite genu "knee;" Greek gony "knee," gōnia "corner, angle;" Latin genu "knee;" Old English cneo, cneow "knee."

Proto-Indo-European root, probably originally "jaw, jawbone," but also forming words for "chin, cheek." It forms all or part of: chin; Compsognathus; gnathic; gnatho-.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit hanuh "jaw," Avestan zanu- "chin;" Armenian cnawt "jawbone, cheek;" Lithuanian žándas "jawbone;" Greek genus "chin, lower jaw," geneion "chin;" Old Irish gin "mouth," Welsh gen "jawbone, chin;" Old English cin, "chin."

Proto-Indo-European root meaning "to gather." 

It forms all or part of: aggregate; aggregation; agora; agoraphobia; allegory; category; congregate; cram; egregious; gregarious; panegyric; paregoric; segregate.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit gramah "heap, troop;" Greek ageirein "to assemble," agora "assembly;" Latin grex "flock, herd," gremium "bosom, lap;" Old Church Slavonic grusti "handful," gramota "heap;" Lithuanian gurgulys "chaos, confusion," gurguolė "crowd, mass;" Old English crammian "press something into something else."

*gerə-, Proto-Indo-European root meaning "to grow old." It forms all or part of: geriatric; geriatrics; gerontocracy; gerontology.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit jara "old age," jarati "makes frail, causes to age;" Avestan zaurvan "old age;" Greek geron "old man;" Ossetic zarond "old man;" Armenian cer "old, old man."

Proto-Indo-European root meaning "to taste; to choose." It forms words for "taste" in Greek and Latin, but its descendants in Germanic and Celtic mostly mean "try" or "choose." The semantic development could have been in either direction.

It forms all or part of: Angus; choice; choose; degustation; disgust; Fergus; gustation; gustatory; gusto; ragout; Valkyrie.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit jus- "enjoy, be pleased;" Avestan zaosa- "pleasure," Old Persian dauš- "enjoy;" Greek geuesthai "to taste;" Latin gustare "to taste, take a little of;" Old English cosan, cesan, Gothic kausjan "to test, to taste of," Old High German koston "try," German kosten "taste of."