envelope

Reading level: hard

Estimated CEFR level: B2 — Upper-Intermediate

Estimated from word frequency; not an official CEFR classification.

Definition

  1. noun a flat (usually rectangular) container for a letter, thin package, etc.
  2. noun any wrapper or covering
  3. noun a curve that is tangent to each of a family of curves

Etymology

PIE word *h₁én From French enveloppe. The engineering sense is derived from flight envelope. The verb is from the noun.

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