noun, noun or participle which takes 'suru', intransitive verb, noun which may take the genitive case particle 'no'
Refers to something currently in vogue, a widespread craze, or general popularity. Can be used as a noun, suru-verb, or no-adjective.
この春はパステルカラーが流行している。
Pastel colors are in fashion this spring.
その
That song became a huge hit among young people.
noun, noun or participle which takes 'suru', intransitive verb
prevalence (of a disease); epidemic
Used specifically for the spread or outbreak of an illness. Often appears in medical or news contexts.
インフルエンザの流行がピークを迎えた。
The influenza epidemic has reached its peak.