What’s the difference between a capitonym and a homonym? Is a capitonym a type of homonym? Or is it something else entirely? Read on to find out more …
A capitonym is a word whose meaning varies according to whether its initial letter is capitalized or not. Capitonyms are often homonyms (words that sound alike but have different meanings) but not always; they’re actually a specific form of homograph (words that share the same spelling but different meanings), and when the two forms are pronounced differently, they’re a form of heteronym (i.e. homographs that have different pronunciations and meanings). Below are some examples; please add any more you can think of to the comments section below (especially if they begin with K, Q, U, V, X, Y or Z …).

Note that many proper names (of people and animals etc. – especially surnames) describe regular nouns and objects when they’re not capitalized (eg. Rose, Violet, Carpenter, Banks, Carol,  Dawn, Baker, etc., and the etymologies are often closely linked — i.e. names are often given after flowers, places etc. and family names are often historically based on professions). An eponym is basically the opposite idea, and another sub-set of capitonyms: it describes a person after whom a discovery, invention, place, etc. is named or thought to be named. Some examples are Bogart, bogart; Curie, curie;  Diesel, diesel; Hector, hector; Hertz, hertz; Hoover, hoover; Joule, joule; Lynch, lynch; Mackintosh, mackintosh; Madeleine, madeleine; Maverick, maverick; Newton, newton; Scrooge, scrooge; Stetson, stetson; Watt, watt; Volt, volt; and Zeppelin, zeppelin.

Some capitonyms:

August (heteronym):
Cap: name. The eighth month of the year
l.c.: adj. Respected and impressive

Bohemian:
Cap: n. A native or inhabitant of Bohemia (now the western part of the Czech Republic)
l.c.: adj. A socially unconventional person, especially one who is involved in the arts

Boxing:
Cap: adj. (British) Boxing Day: A public holiday celebrated on the first day (strictly, the first weekday) after Christmas Day
l.c.: n. The sport or practice of fighting with the fists, especially with padded gloves in a roped square ring according to prescribed rules (the Queensberry Rules)

Cancer:
Cap: n. The fourth sign of the zodiac, which the sun enters at the northern summer solstice (about 21 June). Also, a constellation (the Crab), said to represent a crab crushed under the foot of Hercules. It contains the globular star cluster of Praesepe or the Beehive.
l.c.: n. A disease caused by an uncontrolled division of abnormal cells in a part of the body

Catholic:
Cap: adj. Of the Roman Catholic faith; n. A member of the Roman Catholic Church
l.c.: adj. Including a wide variety of things; all-embracing

Conservative:
Cap: n. A member of the British political Conservative party
l.c.: adj. Averse to change or innovation and holding traditional values.

Divine:
Cap: n. Providence or God
l.c.: adj. Of or like God or a god; v. To discover (something) by guesswork or intuition

Earth
Cap: name: The planet we live on; the world
l.c.: n. The substance of the land surface; soil

Fiat:
Cap: name. An Italian automobile manufacturer.
l.c.: n. A formal authorization or proposition; a decree

Gallic:
Cap: adj. Relating to France or to the ancient territory of Gaul
l.c.: adj. Relating to galls (abnormal plant growths) or gallic acid

Hamlet:
Cap: name. A legendary prince of Denmark, hero of a tragedy by Shakespeare
l.c.: n. A small settlement, generally one smaller than a village, and strictly (in Britain) one without a church

Ionic:
Cap: adj. Relating to or denoting a classical order of architecture characterized by a column with scroll shapes (volutes) on either side of the capital
l.c.: adj. Relating to, composed of, or using ions

Italic:
Cap: adj. Relating to or denoting the branch of Indo-European languages that includes Latin, Oscan, Umbrian, and the Romance languages
l.c.: adj. Of the sloping kind of typeface used especially for emphasis or distinction and in foreign words

Job:
Cap: name: A prosperous man whose patience and piety were tried by undeserved misfortunes, and who, in spite of his bitter lamentations, remained confident in the goodness and justice of God; a book of the Bible telling of Job
l.c.: n. A paid position of regular employment

Lent:
Cap: n. (in the Christian Church) The period preceding Easter, which is devoted to fasting, abstinence, and penitence in commemoration of Christ’s fasting in the wilderness.
l.c.: v. Past and past participle of lend (to grant to someone the use of something on the understanding that it will be returned)

Mandarin:
Cap:  n. The standard literary and official form of Chinese, spoken by over 730 million people; an official in any of the nine top grades of the former imperial Chinese civil service.
l.c.: n. A small flattish citrus fruit with a loose yellow-orange skin.

(Etym: Late 18th century from French mandarine; perhaps related to mandarin, the color of the fruit being likened to the official’s yellow robes.)

March:
Cap: n. The third month of the year
l.c.: v. to walk in a military manner with a regular measured tread;

May:
Cap: n. The fifth month of the year
l.c.: v. Expressing possibility; used to ask for or to give permission; expressing a wish or hope.

Mercury:
Cap: name. The messenger god of Roman mythology, or the first planet in the Solar System
l.c.: n. A substance also known as quicksilver

Mobile: (heteronym)
Cap: name. An industrial city and port on the coast of southern Alabama.
l.c.: adj. Able to move or be moved freely or easily; relating to mobile phones, handheld computers, and similar technology; n. A decorative structure that is suspended so as to turn freely in the air; (British) A mobile phone

Mosaic:
Cap: adj. Of or associated with Moses
l.c.: n. A picture or pattern produced by arranging together small pieces of stone, tile, glass, etc.

Muse:
Cap: n. (in Greek and Roman mythology) Each of nine goddesses, the daughters of Zeus and Mnemosyne, who preside over the arts and sciences.
l.c.: n. A person or personified force who is the source of inspiration for a creative artist.

Nice: (heteronym)
Cap: name. A resort city on the French Riviera, near the border with Italy.
l.c.: adj. Giving pleasure or satisfaction; pleasant or attractive.

Orient:
Cap: n. The countries of the East, especially East Asia.
l.c.: adj. Situated in or belonging to the east; oriental; v. To align or position (something) relative to the points of a compass or other specified positions.

Pentagon:
Cap: name. The pentagonal building serving as the headquarters of the US Department of Defense, near Washington DC.
l.c.: n. A plane figure with five straight sides and five angles.

Polish (heteronym):
Cap: n. Someone from Poland
l.c.: v. To shine the surface of something, or n. the substance used to do this.

Reading:
Cap: name. A town in Berkshire, southern England, on the River Kennet near its junction with the River Thames
l.c.: n. The action or skill of reading; an occasion at which pieces of literature are read to an audience; a particular interpretation of a text or situation;

Scotch:
Cap: adj. Old-fashioned term for Scottish; also n. short for Scotch whisky
l.c.: v. To decisively put an end to.

Turkey:
Cap: name. A country comprising the whole of the Anatolian peninsula in western Asia, with a small portion in south-eastern Europe to the west of Istanbul
l.c.: n. A large mainly domesticated game bird native to North America, having a bald head and (in the male) red wattles. It is a popular food on festive occasions such as Christmas and (in the US) Thanksgiving.

Welsh:
Cap: adj. Relating to Wales, its people, or their language; n. (with “the”) The people of Wales collectively.
l.c.: v. To fail to honor (a debt or obligation incurred through a promise or agreement)

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Hat tip to Lily for introducing me to the capitonym