1 syllable:
'n, -thon, -tion, -xion, .plan, a-one, bklyn, bruhn, brun, brunn, bun, bunn, byun, chian, chron, chthon, chun, chunn, ctc win, dfn win, done, donne, dun, dunn, dunne, fp win, fun, g-men, glsen, gruhn, grun, gun, gunn, h-bahn, he-men, hmgb1, hsian, hslan, huhn, hun, hunn, jrgen, jun, keman, kuhne, kun, llgen, ltgen, luhn, lun, lunn, mun, munn, none, nrcan, nuhn, nun, nunn, one, one-x, phon-, phren, phren-, pkcs1, plzen, prsten, psone, pterin, ptgs1, pun, pv pin, qumran, quqon, rd min, rntgen, run, rvssian, s-plan, shion, shun, skrin, smuin, son, spemann, sphen, sphen-, spun, sq in, sr-71, stian, stun, sun, tcp syn, teman, than, thion-, thran, thron, thrun, thun, ton, tonne, tre mann, trpv1, un, won, wonne, xngine, xp-pen, xtian, youn, yun, zblan

2 syllables:
acfun, air gun, ar-m1, aslan, baekhyun, bank run, begun, blowgun, blue1, bon ton, bren gun, bull run, burp gun, c1, chunyun, close-run, cross bun, cyp1b1, dahyun, dieudonne, doseone, dry run, earned run, end-run, end run, erven, fast one, fcer1, fengyun, fgf21, fine-spun, finespun, first-run, forceone, forerun, fowl run, fresh-run, funrun, fushun, gas gun, gaz-m1, glut1, grandson, greenspun, gross ton, gudrun, h3k4me1, half-done, hamrun, hamsun, handgun, hard-spun, hardspun, hla-dr1, home-run, homerun, homespun, home run, inrun, ithunn, j'kyun, james gunn, john donne, jotunn, kamerun, kaprun, kh-31, kihyun, kofun, kris dunn, lajeune, latrun, lefun, ligue 1, line1, long-run, longspun, long run, long ton, loved one, lushun, m1, macun, make fun, mar-1, mcfun, mcmunn, mean sun, mill-run, misrun, mock sun, moorhuhn, net ton, nipun, nist-f1, noonshun, outdone, outgun, outrun, pashtun, pit run, pl-21, poke fun, porsgrunn, potgun, poynton, pressrun, psk31, pso-1, pushtun, re-run, rebhuhn, redone, rerun, rg-31, rogue one, s5-hvs1, samsun, sean gunn, setun, set gun, sheeprun, shimbun, short-run, short ton, shotgun, ski run, sky one, someone, speedrun, spray gun, spring gun, stepson, sunrun, swimrun, taar1, thyone, triune, undone, unfun, unnun, uprun, vec-m1, wang shun, well-done, well-run, wesun, white1, wing chun, won ton, xbox one, xuyun, yishun, zip gun, zlatan, brian, brien, brion, bryan, bryen, bryon, buyan, buy in, by in, cryan, cryin', cry in, dian, die in, dion, dry in, dye in, flyone, fly in, fry in, gaian, guyon, guy in, gwion, heian, high in, huayan, huyen, ion, kayan, kayane, keihin, leihen, lie in, lion, lionne, lyon, maian, mayan, mion, my in, naion, paien, pie in, pryan, psion, quien, raion, rhian, rion, ryan, ryen, ryon, schneien, schreien, scion, skien, sky in, spy in, thion, tiein, tie in, tryin', tryon, try in, why in, wian, wion, wyan, zeien, zion

3 syllables:
air force one, all-4-one, an/spy-1, andhadhun, anna gunn, anyone, apple m1, august 1, autorun, badayun, bbc one, bisitun, bofors gun, bombing run, cableone, chekhov's gun, chicken run, cyp2e1, dipanjan, dmrt1, efl league one, everyone, for each one, from each one, gatling gun, gau-21, gaz-21, gigaton, giresun, great-grandson, harpoon gun, hired gun, hit-and-run, honey bun, hotdog bun, hot cross bun, jeshurun, kim jong-un, laser-run, lieberkuhn, lotus f1, machine gun, malfunkshun, megaton, megatonne, metric ton, midnight sun, mig-21, mig-31, minute gun, mother's son, naval gun, negaton, number-one, number one, one-on-one, one by one, overdone, overrun, pantsir-s1, pk machine gun, pp-90m1, puget-1, qalawun, quaker gun, rue21, sally lunn, see.sza.run, shadowrun, simeone, sky sports f1, sputnik 1, sta-21, steel ball run, sticky bun, sts-31, terrebonne, tip-and-run, tommy gun, to each one, trappist-1, trappist-1e, trazodone, uhrf1, unbegun, underdone, underrun, unearned run, water gun, whaling gun, achaian, aimyon, akbayan, alion, altaian, ant-lion, ant lion, apply in, aryen, befreien, bisayan, bruneian, cagayan, cairnryan, cantion, chongryon, dacryon, denyen, dicyan, eupryion, euryon, geryon, ghanaian, hawaiian, ixion, jane bryan, johyun, july in, karyon, kedayan, li-ion, luke bryan, mauryan, mcbrien, melion, nvryan, o'brian, o'brien, o'bryan, obrian, obrien, obryan, olayan, ophryon, orion, procyon, reply in, rich brian, sablayan, sea lion, supply in, tropaion, tylion, vinayan, visayan

4 syllables:
2-pyridone, 3rd rock from the sun, ale-8-one, androstenone, are you the one?, band on the run, battlefield 1, bm-21, caramel bun, cinnamon bun, cost overrun, df-21, df-31, electron gun, electryone, favorite son, fifa 21, frankfurter bun, goodnight punpun, hamburger bun, hydrocodone, idra-21, in the long run, july 31, katharine gun, master of none, mclaren f1, mtorc1, nbmr-1, ren21, shenyang fc-31, sts-121, sts-131, submachine gun, the naked gun, tl431, tmsr-lf1, tunguska-m1, vfa-31, vilazodone, voyager 1, williamsf1, zil-131, ahn jae-hyun, alectryon, amphitryon, anakbayan, anthelion, anthocyan, aphid lion, caesarion, celine dion, censorian, chippewaian, condylion, coppelion, dactylion, dandelion, daniel bryan, dikaryon, erechtheion, gerontion, gorgoneion, hellenian, herakleion, herodian, herodion, himalayan, innereien, jeri ryan, jun ji-hyun, kim so-hyun, kim soo-hyun, lee do-hyun, leo ryan, longyearbyen, mesophryon, micoquien, mountain lion, oenocyan, padelion, paraguayan, pommelion, prosodian, prytaneion, pyrocyon, seohyun, signifyin, sk rapid wien, social lion, synkaryon, triskelion, urocyon, uruguayan, xenocyon, xiphoidian

5 syllables:
54321, agenda 21, airbus a321, android 11, antiaircraft gun, area21, bofors 40 mm gun, gw190521, klara and the sun, loadingreadyrun, m-84as1, masayoshi son, mclaren p1, north korean won, ready player one, rpd machine gun, south korean won, tbx21, the old man & the gun, amphikaryon, antibaryon, conan o'brien, dwarf dandelion, dylan o'brien, evangelion, fall dandelion, hemikaryon, hippalectryon, hydrogen ion, hydroxide ion, katherine ryan, leo the lion, liam o'brien, nemean lion, olonkinbyen, perikaryon, ryu sung-hyun, sandiganbayan, steller sea lion

6 syllables:
alpine a521, cx3cr1, deaths in 2021, degtyaryov machine gun, descendants of the sun, eif4ebp1, f1 2021, iodine-131, just dance 2021, m60 machine gun, mikoyan mig-31, mzkt-79221, nba 2k21, thompson submachine gun, unit 731, ammonium ion, australian sea lion, common dandelion, daenerys targaryen, heterokaryon, nimisha sajayan, richard coeur de lion, russian dandelion

7 syllables:
chess world cup 2021, deaths in june 2021, honda in formula one, m240 machine gun, renault in formula one, the house of the rising sun, vmfa-121, california sea lion, march comes in like a lion

8 syllables:
aditayadornkitikhun, deaths in august 2021, deaths in july 2021, m249 light machine gun, miss universe 2021, saturn devouring his son, tornadoes of 2021, california dandelion, monty python's life of brian, south american sea lion, the end of evangelion

9 syllables:
777-9311, aston martin in formula one, bellator mma in 2021, champions chess tour 2021, list of earthquakes in 2021, m1919 browning machine gun, mercedes-benz in formula one, mikoyan-gurevich mig-21, women's chess world cup 2021

10 syllables:
1.1.1.1, alfa romeo in formula one, american airlines flight 11, list of tamil films of 2021, tropical cyclones in 2021, world chess championship 2021, neon genesis evangelion

11 syllables:
eurovision song contest 2021, list of telugu films of 2021, list of tvb dramas in 2021