noun

• The name for the fifth letter of the Greek alphabet, ε or Ε, preceded by delta (Δ, δ) and followed by zeta (Ζ, ζ).
• (phonetics) In IPA, the phonetic symbol ɛ that represents the open-mid front unrounded vowel.
• (mathematics) An arbitrarily small quantity.
• (colloquial) A small child.
• (computing, colloquial) Something negligible or insignificant.
• (finance) The percentage change in an option value with respect to the underlying dividend yield.