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See also: Ium




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



  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. (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!
  4. Used to form the name of an aggregation or mass of something, such as biological tissue: for example, epithelium, pollinium. Words so formed often form their plural with -ia.
  5. Used to indicate the setting where a given activity is carried out: for example, auditorium, colloquium, gymnasium, natatorium, planetarium, podium, sanatorium, stadium. Words so formed often take -a for the plural.

Derived termsEdit

See alsoEdit





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.



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

  1. Suffix used to form abstract nouns, sometimes denoting offices and groups. May no longer be productive.
    auspex + ‎-ium → ‎auspicium
    desiderō + ‎-ium → ‎desiderium
    castellum (castle) + ‎-ium → ‎castilium (fortified city)
  2. (New Latin) Suffix appended to form names of chemical elements.


Second declension.

Case Singular Plural
nominative -ium -ia
genitive -iī
dative -iō -iīs
accusative -ium -ia
ablative -iō -iīs
vocative -ium -ia

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

Derived termsEdit



  1. nominative neuter singular of -ius
  2. accusative masculine singular of -ius
  3. accusative neuter singular of -ius
  4. vocative neuter singular of -ius