# What is meaning of Epsilon or Null in Automata Theory?

In short, epsilon symbol is representation of an empty string.

## What is meaning of epsilon symbol in regular expression

The symbol ε (epsilon) represents the empty string, which is a string that contains no alphabets.

The ε symbol is helpful to read an empty string. For example, Let’s see the given regular expression:

(a)*

This expression means that the alphabet “a” may appear many times or empty string will produce to stop the loop of reading many a’s. The possibility of matching an empty string is also here due to *, because * can produce empty string denoted by ε or many a’s.

## What is meaning of epsilon symbol in Finite automata

The epsilon (ε) symbol represents a transition between states of the finite automata that does not require the consumption of an input symbol. When a state is reached that has an ε-transition, the automaton can make the transition without reading any input symbol. Here input symbol means like symbol 0 or 1, a or b etc.

## What is meaning of epsilon symbol in CFG?

The symbol ε (epsilon) represents the empty string, which is a string that contains no alphabets.

In  CFG, ε is helpful to represent the possibility of a production rule that generates an empty string. For example, Let’s see the given production rule:

A → ε

Its means that the non-terminal symbol A can be replaced with an empty string.

## What is meaning of epsilon symbol in Turing machine?

In Turing machine, the epsilon (ε) symbol represents a blank cell on the tape.

When the Turing machine is initialized and there is no symbols to read then cells of tape are filled with ε symbol. As the machine executes its strings, it reads and writes symbols onto the tape cells, including blank spaces when necessary.