Something I find interesting here is that English consistently uses
adjectives (eg. "the Cretaceous") while German and Swedish use nouns
(_die Kreide_, _krita_, resp.) for segments of geological time. What
do other languages do?
Danish: noun, Icelandic: noun, both Norwegians: noun, Dutch: noun, French:
noun, Spanish: adjective, Portuguese: both, Catalan: apparently noun only,
Italian: both, Breton: noun, Baltic languages: noun, Slavic languages: noun
(but not the same one in all of them), Greek: adjective, Ossetic: apparent
adjective derived from the Russian noun, Hungarian: noun, Turkish: noun,
Vietnamese: I can't figure it out, Indonesian: apparently noun... The
Chinese term starts with "white" and probably ends in a noun ("white-rock
period"?), but how much sense the distinction between nouns and adjectives
makes in Chinese in the first place is AFAIK debatable.