invader
UK: ɪnˈveɪdə | US: ɪnˈveɪdər
n. a person or group that enters a place by force, often to conquer or occupy it
n. an organism that spreads into and disrupts an ecosystem
The word "invader" derives from Latin invadere ("to go into, attack"), combining in- (into) and vadere (to go). The root vad- appears in related words like "evade" (to escape) and "pervade" (to spread throughout). The suffix -er marks the agent (one who performs the action). Historically, "invade" entered Middle English via Old French, later solidifying as "invader" to describe hostile encroachment, whether military, territorial, or ecological.
The Roman army was a formidable invader of neighboring territories.
Invasive species like the zebra mussel are labeled ecological invaders.
Protesters accused the corporation of being an invader of local farmlands.
The castle walls crumbled under the invader's siege weapons.
Scientists study how plant invaders outcompete native species.