-ium

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From Latin -um (neuter singular morphological suffix), based on Latin terms for metals such as ferrum (“iron”).

-ium

1. (chemistry) Used to form the names of metal elements, after the style of early-named elements, as well as the isotopes of hydrogen.
2. (chemistry) Used to form the temporary systematic element name of a metallic or nonmetallic element which is postulated to exist, or which has been newly synthesized and has not yet been assigned a permanent name.
3. (chemistry) Used to form the name of polyatomic cations.
4. (by extension, humorous) Appended to common words to create scientific-sounding or humorous-sounding fictional substance names.
   • 1997, Bryan Pfaffenberger, Official Microsoft Internet Explorer 4 book, page 34:

     According to the FAQ, a site's coolness can be attributed to a trace element called coolium.

   • 2007, Jason Lethcoe, Wishing Well, appendix, page ii:

     Stupidium: Exposure to this Element can cause very silly behavior.

   • 2009, Selena Kitt, Quickies, page 91:

     We're at the North Pole, aren't we? Let's just call the new element Santa Clausium!

Reanalysis from multiple Latin or New Latin compounds suffixed with -ium, whose function, among others, is to derive parasynthetic compounds.

-ium (plural -iums, irregular plural -ia)

2. Used to form the name of an aggregation or mass of something, such as biological tissue

   epithelium, pollinium

4. Forms the name of biological structures and parts.

   clinanthium, periodontium

Reanalysis of Latin words suffixed with -tōrium, -ārium and -ium.

-ium (plural -iums, irregular plual -ia)

1. Used to indicate the setting where a given activity is carried out

   auditorium, gymnasium, planetarium

Reanalysis of ammonium or from -onium of the same source.

-ium

1. (pharmacology) Used to form names of quaternary ammonium compounds used as neuromuscular blocking agents, cholinergic agents, anticholinergic agents, antibacterials/antiseptics, or other agents.

   Alternative form: -onium

• (Etymology 1) -um
• -ion

• IMU, MUI, Miu, Mui, UIM, imu

-ium

1. -ium

From -ius (suffix forming adjectives): as a nominal suffix (Suffix 1), a substantivisation of its neuter forms; as an adjectival suffix (Suffix 2), regularly declined forms. Compare Ancient Greek -ιον (-ion), Proto-Slavic *-ьje.

• (Classical Latin) IPA^(key): /i.um/, [iʊ̃ˑ]
• (modern Italianate Ecclesiastical) IPA^(key): /i.um/, [ium] (stressed on the antepenult)

-ium n (genitive -iī or -ī); second declension

1. Suffix used to form abstract nouns, sometimes denoting offices and groups. May no longer be productive.

   ‎auspex + ‎-ium → ‎auspicium

   ‎dēsīderō + ‎-ium → ‎dēsīderium

   ‎castellum (“castle”) + ‎-ium → ‎castilium (“fortified city”)

2. (New Latin) Suffix appended to form names of chemical elements.

Second-declension noun (neuter).

¹Found in older Latin (until the Augustan Age).

• Norwegian Bokmål: -ium

See the etymology of the corresponding lemma form.

-ium

1. inflection of -ius:
   1. nominative/accusative/vocative neuter singular
   2. accusative masculine singular

See the etymology of the corresponding lemma form.

-ium

1. genitive plural of -s

• “-ium” on page 981/3 of the Oxford Latin Dictionary (1st ed., 1968–82)

From Latin -ium (forms names of chemical elements), from -ius (forms adjectives), from Old Latin -iōs, from Proto-Italic *-jos (forms comparative adverbs), from Proto-Indo-European *-yōs ~ *-is- (forms adjectives).

• IPA^(key): /ɪ.ʉm/

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• Rhymes: -ʉm
• Hyphenation: -i‧um

-ium

2. Used to form nouns (loanwords) of Greek or Latin origin; -ium

   akvarium, evangelium, kriterium, kollegium, laboratorium, medium, privilegium, sanatorium, studium ― aquarium, gospel, criterion, college, laboratory, medium, privilege, sanatorium, study

4. (chemistry) Used to form nouns denoting chemical compounds, especially elements; -ium

   barium, aluminium, beryllium, ammonium ― barium, aluminium, beryllium, ammonium

6. (botany) Used to form nouns denoting plant designations; -ium

   geranium ― geranium

8. (geology) Used to form nouns denoting geological designations; -ium

   alluvium, kambrium, ordovicium ― alluvium, cambrium, ordovicium

• “-ium” in Det Norske Akademis ordbok (NAOB).