Plural of invader; those who enter forcefully into another's territory or domain. Can refer to military forces, unwelcome organisms, or disruptive elements.
From Latin 'invadere' meaning 'to go into, attack', composed of 'in-' (into) + 'vadere' (to go). The military sense is oldest, with biological and metaphorical uses developing later.
The concept of 'invaders' has expanded far beyond warfare to include invasive species in ecology, where plants and animals become 'biological invaders' that disrupt ecosystems. The famous arcade game 'Space Invaders' helped cement the word in popular culture as any threatening external force.
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