prī-, Proto-Indo-European root meaning "to love." In some languages (notably Germanic and Celtic) it developed derivatives with the sense "free, not in bondage," perhaps via "beloved" or "friend" being applied to the free members of one's clan (as opposed to slaves).

It forms all or part of: afraid; affray; filibuster; Frederick; free; freebooter; freedom; friend; Friday; Frigg; Godfrey; Geoffrey; Siegfried; Winfred.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit priyah "own, dear, beloved," priyate "loves;" Old Church Slavonic prijati "to help," prijatelji "friend;" Welsh rhydd "free;" Old English freo "exempt from; not in bondage, acting of one's own will," Gothic frijon "to love," Old English freod "affection, friendship, peace," friga "love," friðu "peace," Old Norse Frigg, name of the wife of Odin, literally "beloved" or "loving."

Proto-Indo-European root meaning "to tear apart, cleave." 

It forms all or part of: cleave (v.1) "to split, part or divide by force;" cleft; clever; clevis; clove (n.2)  "slice of garlic;" glyptodon; hieroglyphic; petroglyph.

It is the hypothetical source of/evidence for its existence is provided by: Greek glyphe "a carving," glyphein "to hollow out, cut out with a knife, engrave, carve;" Latin glubere "to peel, shell, strip;" Old High German klioban, Old English cleofan, Old Norse kljufa "to cleave," Old Norse klofi, Middle Dutch clove "a cleft."  

*sterə-, also *ster-, Proto-Indo-European root meaning "to spread."

It forms all or part of: consternate; consternation; construct; construction; destroy; destruction; industry; instruct; instruction; instrument; obstruct; obstruction; perestroika; prostrate; sternum; sternocleidomastoid; strain (n.2) "race, stock, line;" stratagem; strategy; strath; strato-; stratocracy; stratography; stratosphere; stratum; stratus; straw; stray; street; strew; stroma; structure; substrate; substratum; substructure.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit strnoti "strews, throws down;" Avestan star- "to spread out, stretch out;" Greek stronymi "strew," stroma "bedding, mattress," sternon "breast, breastbone;" Latin sternere "to stretch, extend;" Old Church Slavonic stira, streti "spread," strana "area, region, country;" Russian stroji "order;" Gothic straujan, Old High German strouwen, Old English streowian "to sprinkle, strew;" Old English streon "strain," streaw "straw, that which is scattered;" Old High German stirna "forehead," strala "arrow, lightning bolt;" Old Irish fo-sernaim "spread out," srath "a wide river valley;" Welsh srat "plain."

*kelə-, Proto-Indo-European root meaning "to shout." Perhaps imitative.

It forms all or part of: acclaim; acclamation; Aufklarung; calendar; chiaroscuro; claim; Claire; clairvoyance; clairvoyant; clamor; Clara; claret; clarify; clarinet; clarion; clarity; class; clear; cledonism; conciliate; conciliation; council; declaim; declare; disclaim; ecclesiastic; eclair; exclaim; glair; hale (v.); halyard; intercalate; haul; keelhaul; low (v.); nomenclature; paraclete; proclaim; reclaim; reconcile.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit usakala "cock," literally "dawn-calling;" Latin calare "to announce solemnly, call out," clamare "to cry out, shout, proclaim;" Middle Irish cailech "cock;" Greek kalein "to call," kelados "noise," kledon "report, fame;" Old High German halan "to call;" Old English hlowan "to low, make a noise like a cow;" Lithuanian kalba "language."

Proto-Indo-European root meaning "field;" probably a derivative of root *ag- "to drive, draw out or forth, move."

It forms all or part of: acorn; acre; agrarian; agriculture; agriology; agro-; agronomy; onager; peregrinate; peregrination; peregrine; pilgrim; stavesacre.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit ajras "plain, open country," Greek agros "field," Latin ager (genitive agri) "a field," Gothic akrs, Old English æcer "field."

Proto-Indo-European root meaning "to share out, apportion; to get a share."

It forms all or part of: aphagia; Bhagavad-Gita; baksheesh; esophagus; nebbish; pagoda; -phage; phago-; -phagous; porgy; sarcophagus.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit bhajati "assigns, allots, apportions, enjoys, loves," bhagah "allotter, distributor, master, lord," bhaksati "eats, drinks, enjoys;" Persian bakhshidan "to give;" Greek phagein "to eat," literally "to have a share of food;" Old Church Slavonic bogatu "rich."

*petə-, Proto-Indo-European root meaning "to spread."

It forms all or part of: compass; El Paso; expand; expanse; expansion; expansive; fathom; pace (n.); paella; pan (n.); pandiculation; pas; pass; passe; passim; passacaglia; passage; passenger; passport; paten; patent; patina; petal; spandrel; spawn.

It is the hypothetical source of/evidence for its existence is provided by: Greek petannynai "to spread out," petalon "a leaf," patane "plate, dish;" Old Norse faðmr "embrace, bosom," Old English fæðm "embrace, bosom, fathom," Old Saxon fathmos "the outstretched arms."

Proto-Indo-European root meaning "to shoot, chase, throw."

It forms all or part of: scot-free; scout (v.2) "to reject with scorn;" sheet (n.1) "cloth, covering;" sheet (n.2) "rope that controls a sail;" shoot; shot; shout; shut; shuttle; skeet; wainscot.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit skundate "hastens, makes haste;" Old Church Slavonic iskydati "to throw out;" Lithuanian skudrus "quick, nimble;" Old English sceotan "to hurl missiles," Old Norse skjota "to shoot with (a weapon)."

*keuə-, Proto-Indo-European root meaning "to swell," also "vault, hole."

It forms all or part of: accumulate; accumulation; cave; cavern; cavity; coeliac; church; codeine; coelacanth; coeliac; coelomate; concave; cumulate; cumulative; cumulus; enceinte; excavate; kirk; kymatology; Kyrie eleison.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit svayati "swells up, is strong;" Greek kyein "to swell," koilos "hollow, hollowed out, spacious, deep;" Latin cumulus "a heap, pile, mass, surplus;" Lithuanian šaunas "firm, solid, fit, capable;" Middle Irish cua "hollow;" Armenian soyl "cavity."

Proto-Indo-European root meaning "to collect, gather," with derivatives meaning "to speak" on the notion of "to gather words, to pick out words."

It forms all or part of: alexia; analects; analogous; analogue; analogy; anthology; apologetic; apologue; apology; catalogue; coil; colleague; collect; college; collegial; Decalogue; delegate; dialect; dialogue; diligence; doxology; dyslexia; eclectic; eclogue; elect; election; epilogue; hapax legomenon; homologous; horology; ideologue; idiolect; intelligence; lectern; lectio difficilior; lection; lector; lecture; leech (n.2) "physician;" legacy; legal; legate; legend; legible; legion; legislator; legitimate; lesson; lexicon; ligneous; ligni-; logarithm; logic; logistic; logo-; logogriph; logopoeia; Logos; -logue; -logy; loyal; monologue; neglect; neologism; philology; privilege; prolegomenon; prologue; relegate; sacrilege; select; syllogism; tautology; trilogy.

It is the hypothetical source of/evidence for its existence is provided by: Greek legein "to say, tell, speak, declare; to count," originally, in Homer, "to pick out, select, collect, enumerate;" lexis "speech, diction;" logos "word, speech, thought, account;" Latin legere "to gather, choose, pluck; read," lignum "wood, firewood," literally "that which is gathered," legare "to depute, commission, charge," lex "law" (perhaps "collection of rules"); Albanian mb-ledh "to collect, harvest;" Gothic lisan "to collect, harvest," Lithuanian lesti "to pick, eat picking;" Hittite less-zi "to pick, gather."