出典:Wiktionary
出典:『Wiktionary』 (2025/08/10 17:55 UTC 版)
Uncertain. Possibly from the Latin infra (“below”) and diēs (“a day”) with the English suffix -an. Compare circadian, ultradian, and infra etc.
infradian (not comparable)
The comparative "more infradian" is not used, in contrast to the comparative "more ultradian".