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

-ium

1. (chemistry)Used to form the names of metalelements, after the style of early-named elements, as well as theisotopes ofhydrogen.
2. (chemistry)Used to form thetemporarysystematic element name of ametallic ornonmetallic element which ispostulated to exist, or which has been newlysynthesized and has not yet beenassigned apermanent name.
3. (chemistry)Used to form the name ofpolyatomiccations.
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, page34:

     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, page91:

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

Reanalysis from multipleLatin orNew Latin compounds suffixed with-ium, whose function, among others, is to deriveparasyntheticcompounds.

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

2. Used to form the name of anaggregation ormass of something, such asbiologicaltissue

   epithelium,pollinium

4. Forms the name of biologicalstructures and parts.

   clinanthium,periodontium

Reanalysis ofLatin 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 ofammonium or from-onium of the same source.

-ium

1. (pharmacology)Used to form names ofquaternary ammonium compounds used asneuromuscular blocking agents,cholinergicagents,anticholinergic agents,antibacterials/antiseptics, or other agents.

   Alternative form:-onium

• (Etymology 1)-um
• -ion

• IMU,MUI,Miu,Mui,UIM,imu

-ium

2. Used to formnouns (loanwords) ofGreek orLatin origin;-ium

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

4. (chemistry)Used to formnouns denotingchemical compounds, especiallyelements;-ium

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

6. (botany)Used to formnouns denotingplant designations;-ium

   geranium,kaprifolium ―caprifolium, geranium

• “-ium” inDen Danske Ordbog

-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. CompareAncient 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-iīor-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 correspondinglemma form.

-ium

1. inflection of-ius:
   1. nominative/accusative/vocativeneutersingular
   2. accusativemasculinesingular

See the etymology of the correspondinglemma form.

-ium

1. genitiveplural of-s

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

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

• IPA^(key):/ɪ.ʉm/

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• Rhymes:-ʉm
• Hyphenation:-i‧um

-ium

2. Used to formnouns (loanwords) ofGreek orLatin origin;-ium

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

4. (chemistry)Used to formnouns denotingchemical compounds, especiallyelements;-ium

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

6. (botany)Used to formnouns denotingplant designations;-ium

   geranium ―geranium

8. (geology)Used to formnouns denotinggeological designations;-ium

   alluvium, kambrium, ordovicium ―alluvium, cambrium, ordovicium

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