Empty String

Empty String ($\epsilon$)

• Definition: The empty string is the unique String with length zero. It functions as an
• Notation:
  • Symbol: $\epsilon$
  • Sometimes also written as $\lambda$ or just "".
• Properties:
  • $|\epsilon |=0$ (length is zero).
  • For any string $s$: $s\cdot \epsilon =\epsilon \cdot s=s$ ($\epsilon$ is the identity element for string concatenation).