LATIN DICTIONARYLexicon Latīnum
suffixfirst/second-declension suffix

-urnus

-urnus (feminine -urna, neuter -urnum)
Classical[ʊr.nʊs]Ecclesiastical[ur.nus]

Meaning

  1. morphemesuffixEnlargement of -nus (suffix forming adjectives).
    albus + -urnus → alburnus
    diū (comparative stem: diūt-) + -urnus → diūturnus

Origins

Ultimately from the adjective-forming suffix -(i)nus; see also -rnus. Szemerényi 1959 proposes that the starting point was pre-Latin *hesterinos (hesternus) and *wesperinos (reconstructed based on the obsolete word vesperna). As a result of rebracketing, the *-erinos at the end of these words would have been attached to *diw- and *nokt-, the pre-Latin roots of the words diēs (“day”) and nox (“night”), initially forming *diw-erinos and *nokt-erinos. Szemerényi argues that *diw-erinos was syncopated to *diwrinos and then regularly developed to *diurnos (Latin diurnus), and then the ending *-urnos was extended by analogy to nocturnus and other words. Others have argued that the adjectives may have been formed on or influenced by the adverbs diū/diūs (“by day”) and noctū (“at night”).

Quick answers

What does -urnus mean in Latin?
-urnus, a suffix, means “Enlargement of -nus (suffix forming adjectives).”.
How do you pronounce -urnus?
In classical Latin, [ʊr.nʊs]; in ecclesiastical (church) Latin, [ur.nus].