Machina improba! Vel mihi ede potum vel mihi redde nummos meos! - You infernal machine! Give me a beverage or give me my money back!

　　Maecenas atavis edite regibus - Maecenas, born of monarch ancestors. (Horace)

　　Magister artis ingeniique largitor venter - Necessity is the mother of all invention

　　Magister Artium (MA) - Master of arts

　　Magister mundi sum! - I am the master of the universe!

　　Magna charta - Great paper

　　Magna cum laude - With great honour or academic distinction

　　Magna res est vocis et silentii temperamentum - The great thing is to know when to speak and when to keep quiet

　　Magnas inter oper inops - A pauper in the midst of wealth. (Horace)

　　Magnificat - It magnifies

　　Magnum bonum - A great good

　　Magnum opus - Great work, the major work of one's life

　　Magnus frater spectat te - Big Brother is watching you

　　Maior risus, acrior ensis: quadragesima octava regula quaesitus - The bigger the smile, the sharper the knife: the 48th rule of acquisition

　　Mala fide - In bad faith (something which is done fraudulently)

　　Male parta male dilabuntur - What has been wrongly gained is wrongly lost. (Ill-gotten gains seldom prosper.) (Cicero)

　　Malum consilium quod mutari non potest - It's a bad plan that can't be changed. (Publilius Syrus)

　　Malum prohibitum - A prohibited wrong. A crime that society decides is wrong for some reason, not inherently evil

　　Malum quidem nullum esse sine aliquo bono - There is, to be sure, no evil without something good. (Pliny the Elder)

　　Manus in mano - Hand in hand

　　Manus manum lavat - One hand washes the other. The favor for the favor. (Petronius)

　　Mare clausum - A closed sea

　　Mare liberum - An open sea

　　Mare nostrum - Our sea. (Mediterranean)

　　Margaritas ante porcos - Pearls before swine. To give something valuable to someone not respecting it

　　Mater artium necessitas - Necessity is the mother of invention

　　Mater dolorosa - Sorrowful mother. (Virgin Mary)

　　Mater memento mori - Remember your mortality

　　Mater tua criceta fuit, et pater tuo redoluit bacarum sambucus - Your mother was a hamster and your father smelt of elderberries

　　Mater - Mother

　　Materfamilias - Mother of family

　　Materia medica - Medical matter

　　Materiam superabat opus - The workmanship was better than the subject matter. (Ovid)

　　Maxima debetur puero reverentia - We owe the greatest respect to a child

　　Maximus in minimis - Great in little things

　　Me fallit - I do not know

　　Me iudice - I being judge; in my judgement

　　Me oportet propter praeceptum te nocere - I'm going to have to hurt you on principle

　　Me transmitte sursum, caledoni! - Beam me up, Scotty!

　　Mea culpa - Through my fault

　　Mea maxima culpa - Through my very great fault

　　Mea mihi conscientia pluris est quam omnium sermo - My conscience means more to me than all speech. (Cicero)

　　Medice, cura te ipsum! - Physician, heal thyself! (Versio Vulgata)

　　Medici graviores morbos asperis remediis curant - Doctors cure the more serious diseases with harsh remedies. (Curtius Rufus)

　　Medicus curat, natura sanat - The physician treats, nature cures

　　Medio tutissimus ibis - You will go safest in the middle. (Moderation in all things) (Ovid)

　　Mei capilli sunt flagrantes - My hair is on fire

　　Meliora cogito - I strive for the best

　　Melitae amor - Love of Malta

　　Melius est praevenire quam praeveniri - Better to forestall than to be forestalled

　　Melius frangi quam flecti - It is better to break than to bend

　　Melius tarde, quam nunquam - Better late than never

　　Mellita, domi adsum - Honey, I'm home

　　Memento mori - Remember that you must die

　　Memento vivere - A reminder of life (literally remember that you have to live)

　　Memorabilia - Memorable things

　　Memorandum - A note of; a thing to be remembered

　　Memoria in aeterna - In everlasting remembrance

　　Memoriter - From memory

　　Mendacem memorem esse oportet - A liar needs a good memory. (Quintilianus)

　　Mens agitat molem - The mind moves the matter. (Vergil)

　　Mens rea - Guilty mind

　　Mens regnum bona possidet - An honest heart is a kingdom in itself. (Seneca)

　　Mens sana in corpore sano - A sound mind in a sound body. (Juvenalis)

　　Mens sibi conscia recti - A mind conscious of its rectitude

　　Meum cerebrum nocet - My brain hurts

　　Meum pactum dictum - My word is my bond

　　Mihi cura futuri - My concern is the future

　　Mihi ignosce. Cum homine de cane debeo congredi - Excuse me. I've got to see a man about a dog

　　Millennium (millennia) - A thousand year period

　　Minime senuisti! - You haven't aged a bit!

　　Minus habens - Absentminded

　　Mirabile dictu - Wonderful to say/relate. (Vergil)

　　Mirabile visu - Wonderful to behold

　　Miserere - Have mercy

　　Missa solemnis - Solemn Mass. (high Mass)

　　Mittimus - We send (to prison)

　　Modus agendi - Manner of operation

　　Modus operandi (m.o.) - Way of operating

　　Modus vivendi - Way of living

　　Monstra mihi pecuniam! - Show me the money!

　　Moratorium - A delay

　　Morituri te salutant - Those who are about to die salute you

　　Mors ultima linea rerum est - Death is everything's final limit. (Horace)

　　Mors ultima ratio - Death is the final accounting

　　Mortvi non mordant - Dead me don't bite; Dead men tell no tale

　　Motu proprio - Of one's own initiative

　　Mulier taceat in ecclesia - Let the woman be silent in church. (Paul)

　　Multi famam, conscientiam pauci verentur - Many fear their reputation, few their conscience. (Pliny)

　　Multis post annis - Many years later

　　Multum in parvo - Much in little. (small but significant)

　　Multun, non multa - Much, not many (quality not quantity)

　　Mundus vult decipi, ergo decipiatur - The world wants to be deceived, so let it be deceived!

　　Mundus vult decipi - The world wants to be deceived

　　Munit haec et altera vincit - One defends and the other conquers

　　Mus uni non fidit antro - A mouse does not rely on just one hole. (Plautus)

　　Musica delenit bestiam feram - Music soothes the savage beast

　　Mutatis mutandis - The necessary changes having been made

　　Mutato nomine - The name being changed

　　Mvlti svnt vocati, pavci vero electi - Many are called [but] few are chosen

　　Mvndvs vvlt decipi - The world wishes to be deceived there's a sucker born every minute

　　Mvtatis mvtandis - The things that ought to have changed having been changed with the necessary substitutions having been made