-onym

Morphemes with the affix -onym are designations for either a closed set of grammatical morphemes that refer to relationships between word pairs, such as synonym and antonym; or they may stand for classical compound nouns of an open type that refer to a particular subject, such a toponym, characternym, etc. By analogy they may be freely created, sometimes for no other reason than to give an erudite impression of the user who expects his listeners to understand Greek, and it is in this way that words such as ornithonym or ichthyonym may be formed.

The usage of the word pairs is of great importance in grammar. Some morphemes ending in -onym may represent words that contain components, in the way house may contain window, roof, and door, or they may be words so contained in others, such as steering-wheel and engine in car.
They may be generic words that stand for a class or group of equally-ranked items, such as tree for beech or elm, or belong within that class, such as lily or violet in flower.
They may have the same or a similar meaning as a differently spelled word, such as sofa or couch, or they may stand in direct contrast to another, such as useful and useless.

Some morphemes have the -nym form rather than the -onym form, such as characternym, or hypernym but that may be more for ease of pronunciation than for etymological reasons.

Most -onyms may have suffixes added to them and in this way form derivatives with the endings -onymy, -onymous, - onymic, etc., in new constructions. Others may reverse this process by removing suffixes in back-formations, especially if the new morphemes thus formed sound plausible enough to have been the root form in first place.

A list of -onym words

• acronym - an abbreviation formed from the initials of one or more words that is pronouncable like a normal word, such as NATO
• allonym - an author's name of another person's, often a well-known person's name
• anacronym - portmanteau morpheme of anachronism+ acronym that may be an acronym, abbreviation, or initialism but that is so well established that its origin is no longer remembered. As this seems a specious reason (after all any acronym may be looked up in a dictionary) it may be more applicable to abbreviations, etc., that are at risk of becoming out-of-date and being superseded by newer abbreviations, such as AD being replaced by CE (Common Era)
• anonym - word defining anything created anonymously, or the person who has created it; an unknown author; a pseudonym
• antonym - one of the words of the word pair antonym and synonym that indicates the exact opposite meaning of another word, such as high and low
• aptronym - name appropriate to its owner's occupation or physical properties as in Goldsmith or Longman
• aristonym - one of the classical compound nouns of -onym words that denotes a name that is derived from a high rank or a title of nobility
• backronym - portmanteau morpheme of back + acronym that appears to fit an existing word but has really been created as an acronym, such as BASIC (Beginner's All-purpose Symbolic Instruction Code)
• caconym - one of the words of the word pair caconym and euonym; a word that is wrongly applied; a misnomer; the incorrect name for something, especially in the classification of plants, etc.
• capitonym - word that changes its pronunciation and meaning when it is capitalized, and usually applies to capitalization due to proper names or eponyms, as in August - august, or Polish - polish
• characternym - name of a fictional character that may be reflected in his personality, as in Shakespeare's Pistol or Bottom
• contronym - a word that may have opposite meanings in different contexts, such as to cleave - to stick, adhere, and to cleave - to split
• cryptonym - a classical compound noun as a code name; a word or name used clandestinely to refer to another name or word
• demonym - one of the classical compound nouns, a name of persons/people that refers to the place they come from, such as the Assyrian, or the Briton
• eponym - a botanical, zoological or place name that derives from a real or legendary person; a name for a real of hypothetical person from whom a botanical, geographical or zoological name is derived; a person after whom a medical condition is named
• euonym - one of the words of the word pair euonym - caconym; a word well suited to a person, place or thing so named; a pleasant name
• exonym - a name used by one group of people for another group, but who call themselves by a different name, such as the name Germans used by English-speakers for Deutsche the name German-speakers use
• heteronym - one of the words of the word pair homonym and heteronym; a word that is spelled in the same way as another but that has a different sound and meaning, such as bow of the ship and bow and arrow.
• holonym - one word of the word pair holonym and meronym; a word for the whole and of which other words are part, in the way house contains roof, door and window; or car comprises steering-wheel and engine

Work in progress