A plural form of aecidium, referring to multiple cup-shaped structures on infected plant leaves where rust fungi produce their spores.
Latin plural of aecidium, which itself comes from Greek aikia (αἰκία, 'damage'). The spelling 'aecidia' represents the standard Latinized Greek plural used in scientific nomenclature.
When you see bright orange or yellow cup-shaped pustules on a leaf, you're looking at rust aecidia producing millions of spores—historically, farmers had no idea these were the sexual reproductive stage of a fungus, they just knew it meant their crops were dying.
Complete word intelligence in one call. Free tier — 50 lookups/day.