Proto-Indo-European root meaning "to let go, slacken." 

It forms all or part of: alas; allegiance; lassitude; last (adj.) "following all others;" late; latter; lenient; lenitive; lenity; let (v.) "allow;" let (n.) "stoppage, obstruction;" liege.

It is the hypothetical source of/evidence for its existence is provided by: Greek ledein "to be weary;" Latin lenis "mild, gentle, calm," lassus "faint, weary;" Lithuanian lėnas "quiet, tranquil, tame, slow," leisti "to let, to let loose;" Old Church Slavonic lena "lazy," Old English læt "sluggish, slow," lætan "to leave behind." 

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."

Proto-Indo-European root meaning "to lie down, lay."

It forms all or part of: allay; anlage; belay; beleaguer; bylaw; coverlet; fellow; lager; lair; law; lawful; lawless; lawsuit; lawyer; lay (v.) "to cause to lie or rest;" ledge; ledger; lees; lie (v.2) "rest horizontally;" litter; lochia; low (adj.) "not high;" outlaw; scofflaw; stalag; vorlage.

It is the hypothetical source of/evidence for its existence is provided by: Hittite laggari "falls, lies;" Greek lekhesthai "to lie down," legos "bed," lokhos "lying in wait, ambush," alokhos "bedfellow, wife;" Latin lectus "bed;" Old Church Slavonic lego "to lie down;" Lithuanian at-lagai "fallow land;" Old Irish laigim "I lie down," Irish luighe "couch, grave;" Old English licgan "be situated, have a specific position; remain; be at rest, lie down."

Proto-Indo-European root meaning "not heavy, having little weight."

It forms all or part of: alleviate; alleviation; alto-rilievo; carnival; elevate; elevation; elevator; leaven; legerdemain; leprechaun; Levant; levator; levee; lever; levity; levy (v.) "to raise or collect;" light (adj.1) "not heavy, having little weight;" lighter (n.1) "type of barge used in unloading;" lung; relevance; relevant; releve; relief; relieve.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit laghuh "quick, small;" Greek elakhys "small," elaphros "light;" Latin levare "to raise," levis "light in weight, not heavy;" Old Church Slavonic liguku, Russian lëgkij, Polish lekki, Lithuanian lengvas "light in weight;" Old Irish lu "small," laigiu "smaller, worse;" Gothic leihts, Old English leoht "not heavy, light in weight."

Proto-Indo-European root meaning "to tie, bind." 

It forms all or part of: alloy; ally; colligate; deligate; furl; league (n.1) "alliance;" legato; liable; liaison; lien; lictor; ligand; ligament; ligate; ligation; ligature; oblige; rally (v.1) "bring together;" religion; rely.

It is the hypothetical source of/evidence for its existence is provided by: Latin ligare "to bind;" Albanian lidh "I bind," and possibly Middle Low German lik "band," Middle High German geleich "joint, limb."

Proto-Indo-European root meaning "to lick." It forms all or part of: cunnilingus; lecher; lichen; lick.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit ledhi "he licks," Armenian lizum "I lick," Greek leikhein "to lick," Latin lingere "to lick," Old Irish ligim "I lick," Welsh llwy "spoon," Old English liccian "to lick."

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

It forms all or part of: delinquent; derelict; eclipse; eleven; ellipse; ellipsis; elliptic; lipo- (2) "lacking;" lipogram; loan; paralipsis; relic; relict; reliction; relinquish; reliquiae; twelve.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit reknas "inheritance, wealth," rinakti "leaves;" Greek leipein "to leave, be lacking;" Latin linquere "to leave;" Gothic leihvan, Old English lænan "to lend;" Old High German lihan "to borrow;" Old Norse lan "loan."

Proto-Indo-European root meaning "to stick, adhere; fat."

It forms all or part of: adipose; beleave; delay; leave (v.); lebensraum; life; liparo-; lipo- (1) "fat;" lipoma; liposuction; lively; live (v.); liver (n.1) "secreting organ of the body;" Olaf; relay.

It is the hypothetical source of/evidence for its existence is provided by: Greek liparein "to persist, persevere," aleiphein "anoint with oil," lipos "fat;" Old English lifer "liver," læfan "to allow to remain."

Proto-Indo-European root meaning "to loosen, divide, cut apart."

It forms all or part of: absolute; absolution; absolve; analysis; analytic; catalysis; catalyst; catalytic; dialysis; dissolve; electrolysis; electrolyte; forlorn; Hippolytus; hydrolysis; -less; loess; loose; lorn; lose; loss; Lysander; lysergic; lysis; -lysis; lyso-; lysol; lytic; -lytic; palsy; paralysis; pyrolusite; resolute; resolution; resolve; soluble; solute; solution; solve; solvent.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit lunati "cuts, cuts off," lavitram "sickle;" Greek lyein "to loosen, untie, slacken," lysus "a loosening;" Latin luere "to loose, release, atone for, expiate;" Old Norse lauss "loose, free, unencumbered; vacant; dissolute;" Old English losian "be lost, perish."

Proto-Indo-European root meaning "to care, desire, love."

It forms all or part of: belief; believe; furlough; leave (n.) "permission, liberty granted to do something;" leman; libido; lief; livelong; love; lovely; quodlibet.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit lubhyati "desires," lobhaya- "to make crazy;" Persian ahiftan "to be tangled, be hit down, be in love;" Latin lubet, later libet "pleases," libido, lubido "desire, longing; sensual passion, lust;" Old Church Slavonic l'ubu "dear, beloved," ljubiti, Russian ljubit' "to love;" Lithuanian liaupsė "song of praise;" Old English lufu "feeling of love; romantic sexual attraction," German Liebe "love," Gothic liufs "dear, beloved."