Double trouble

Schoolchildren learn to double the final consonant of one-syllable words before the suffixes -ing, -ed, -en, -er, -y or -ish (e.g. bat - batting, batted, batty, batter; snob – snobbish, rot – rotten) to show that the preceding stressed vowel is short, instead of long, as in ‘bate, bated, bating’. With one-syllable words this rule is used consistently, but longer verbs can have doubled consonants before suffixes even when the preceding vowel is not stressed: benefitted, travelled – preferred, permitted.

In longer root words, English consonant doubling is totally random:
372 words (e.g. mellow) have a doubled consonant after a short, stressed vowel
384 words (e.g. melon) disobey the doubling rule     and
158 words (e.g. satellite) have unpredictable doubled consonants after unstressed vowels.
The words below show how much rote-learning the unpredictability of English consonant doubling creates.
Consistent use of the doubling rule would make this unnecessary.

Abbey, cabbage, jabber, rabbit, Sabbath, shabby, ribbon, hobby, lobby, chubby, rubber, rubbish, stubborn, stubby.
Cabinet, cabaret, cabin, elaborate, fabulous, habit, nebula, treble, liberal, liberty, tribute, probable, robin.
Abbreviate.

(For a k-sound after a short vowel ck is the main spelling.)
Bracken, bracket, jacket, packet, package, racket, reckon, bicker, chicken, cricket, flicker, rickety, sticky, ticket, wicked, wicker, wicket, cockerel, crockery, hockey, jockey, locket, pocket, rocket, rocky, socket, stocking, bucket, sucker, cuckoo.
Vacuum, accurate, tobacco, lacquer, decade, executive, recognise, record (noun), second, secular, echo, mechanism, chequered, piccolo, liquor, liquorice, crocodile, documents, occupy, succulent.
Accommodate, accommodation, accompany, accomplish, accord, accordion, account, accumulate, accuse, accustom, occasion, occupation, occurrence, succumb.

Adder, caddie, caddy, daddy, ladder, eddy, teddy, wedding, giddy, hidden, ridden, shoddy, sodden, rudder, shudder, sudden, pudding.
Academy, adequate, radical, radish, credit, dedicated, edible, edit, educate, federal, medical, pedal, pedigree, meadow, ready, already, steady, hideous, video, body, modern, modest, produce (noun), study.

Daffodil, scaffold, traffic, effigy, effort, different, difficult, jiffy, coffee, coffin, offer, office, buffalo, buffer, buffet, chuffed, ruffian, suffer, suffocate.
Café, refuge, refuse (noun), heifer, magnificent, significant, profit.
Affair, affect, affection, afford, paraffin, effect, efficient, differential, diffusion, offend, official, sufficient, chauffeur.

Baggage, jagged, maggot, scraggy, stagger, swagger, beggar, snigger, trigger, soggy, luggage, nugget, rugged.
Agony, dragon, flagon, hexagonal, negative, brigand, frigate.
Aggressive.

Badger, fledgling, midget, dodgems, dodgy, podgy, budgie, budget, drudgery.
Exaggerate, legend, legislate, regiment, register, vegetable, digit, pigeon, religion, rigid, logic.
Suggest (Can be [sugjest] in US.)

Alley, alligator, ally, ballast, ballet, ballot, challenge, gallant, gallery, gallon, gallop, gallows, mallet, rally, shallow, stallion, valley, bellow, belly, cellar, cello, cellophane, fellow, intelligent, jelly, pellet, rebellion, sellotape, trellis, umbrella, yellow, armadillo, artillery, billiard, billion, billow, billy, brilliant, frilly, gorilla, guerrillas, guillotine, illustrate, milligrams, million, pillar, pillow, silly, syllable, vanilla, villa, village, villain, collar, colleague, collie, colliery, dollar, follow, hollow, holly, jolly, lollipop, lolly, mollusc, pollen, pollinate, trolley, volley, college, swallow, wallaby, wallet, wallop, wallow, lullaby, sullen, bullet, bulletin, bullion, bullock, bully, pulley, pullover.
Analysis, balance, battalion, calendar, chalet, galaxy, italic, morality, palace, palate, palette, reality, salad, salary, salon, talent, talon, valentine, valiant, valid, value, vitality, celery, delegate, delicacy, deluge, develop, element, eligible, helicopter, jealous, melody, melon, pelican, relevant, relic, skeleton, telescope, zealous, ability, bilious, military, ventriloquist, cylinder, abolish, colony, column, demolish, holiday, olive, policy, politics, polythene, solemn, solid, tolerate, volume, voluntary, knowledge, quality, colour.
Llama, parallel, excellent, hello, jewellery, marvellous, satellite, constellation, caterpillar, illegible, illiterate, illusion, illustration, illuminate, pastille, tonsillitis, collage, collapse, collect, collide.
With long, instead of short vowels: controlled, roller, swollen.

Ammonite, clammy, hammer, inflammable, mammal, mammoth, stammer, dilemma, glimmer, simmer, symmetry, comment, commentary, commerce, common, communism, communist, dummy, mummy, rummage, summary, summer, summit, summon, tummy.
Amateur, camel, camera, damage, dynamic, enamel, famished, laminate, cemetery, chemical, democrat, emerald, epidemic, memory, remedy, lemon, feminine, premise, semi, criminal, eliminate, image, limit, timid, women, abominable, comet, comic, dominate, domino, economic, prominent, promise, vomit, stomach, plumber.
Ammunition, programme, immediate, immense, immortal, immune, command, commemorate, commence, commercial, commit, commodities, commotion, communication, communion, community, commuter, committee, recommend.

Annual, banner, cannot, granny, manner, nanny, pannier, savannah, spanner, uncanny, antenna, pennant, tennis, penny, dinner, inner, innocence, innocent, spinnaker, bonnet, sonnet, bunny.
Animal, anorak, banish, banister, canopy, manage, manor, manual, organic, panel, panic, spaniel, vanish, benefit, enemy, energy, menace, penetrate, venison, lieutenant, any, many, aluminium, clinical, continue, finish, linear, minimal, minister, opinion, sinister, spinach, vinegar, cinema, cynical, synagogue, synonym, minute (minnit), astonish, conifer, economy, electronic, monastery, monarch, monument, supersonic, tonic, honey, money, onion, punish.
Anniversary, announce, annoy, connect, personnel, mayonnaise, questionnaire.

Appetite, happen, happy, nappy, pepper, flipper, kipper, skipper, slipper, copper, coppice, opposite, poppy, sloppy, puppet, puppy, supper, upper.
Capital, capitol, rapid, tapestry, capita, epic, jeopardy, leper, leopard, tepid, separate, weapon, copy, opera, operate, proper, property, topic, popular, tropics.
Appal, apparatus, apparent, appeal, appear, appendix, applaud, apply, appoint, appreciate, apprentice, approach, appropriate, approve, approximate, hippopotamus, opportunity, oppose, suppose, supply, support.

Arrow, barren, barrier, barrister, barrow, carrot, carry, garret, marrow, marry, narrative, narrow, parrot, sparrow, merry, sherry, terrace, terrible, territory, terror, irritable, mirror, squirrel, stirrup, borrow, corridor, horrible, lorry, porridge, sorrow, sorry, tomorrow, torrent, quarry, warrant, warren, burrow, current, furrowed, hurricane, hurry, scurry, turret, worry, furry.
Arab, arable, arid, asparagus, baron, caramel, caravan, caricature, carol, chariot, charity, clarity, comparison, parasol, parish, transparent, America, beret, ceremony, cherish, derelict, herald, heritage, heroine, heron, merit, peril, perish, sincerity, sterilise, therapist, very, bury, conspiracy, empirical, lyric, miracle, spirit, syrup, tyranny, authority, coral, florist, forest, historic, horoscope, majority, minority, moral, orange, priority, laurel, quarantine, thorough, courage, nourish.
Arrange, array, arrest, arrive, barricade, erratic, interrupt, serrated, terrific, irregular, irrigation, torrential, correspond, correct, correlation, curriculum, surrender, surround, hurrah.

Ambassador, casserole, classic, massacre, massive, passage, passenger, delicatessen, essay, essence, lesson, message, necessity, professor, missile, narcissus, rissole, blossom, colossal, fossil, gossip, possible.
Acid, capacity, pacifist, glacier (US glaishier), fascinate, decimal, precipice, necessary, recipe, specify, specimen, adolescent, convalescent, crescent, discipline, chrysalis, electricity, explicit, municipal, participate, publicity, simplicity, solicitor, velocity, sausage.
Assail, assassin, embassy, assault, assemble, assert, assessment, assign, assist, associate, assort, assume, cassette, dessert, essential, possess, possibility.

Attic, attitude, batter, battery, chatter, clatter, fatty, matter, patter, pattern, regatta, scatter, shatter, tatter, latter, better, confetti, jettison, jetty, letter, lettuce, spaghetti, bitten, bitter, glitter, kitten, litter, mitten, pretty, sitter, titter, twitter, written, bottom, cottage, cotton, forgotten, lottery, motto, otter, potter, butter, button, clutter, gutter, mutter, mutton, putty, shutter, splutter, stutter, utter.
Atom, baton, catalogue, catapult, category, compatible, lateral, latitude, platinum, platypus, satin, strategy, athletic, magnetic, metal, petal, tetanus, veteran, yeti, competitive, British, citizen, city, critical, pity, literally, obliterate, botany.
Attach, attain, attempt, attend, attention, attorney, attract, attributed, battalion, tattoo, mattress, omelette, palette, settee.

Blizzard, dizzy, buzzard.
Hazard, desert, designate, desolate, hesitate, peasant, pheasant, pleasant, present, president, resident, lizard, miserable, prison, risen, visible, visit, scissors, wizard, wizened, lozenge, closet, deposit, positive.