**Define the following terms with example :**__A "symbol" is an abstract entity that we shall not define formally, just as "point" and "line" are not defined geometry__

**(i) Symbols :**__a,b,c etc are alphabetical symbols, 1,2,3 etc are numerical symbols.__

**Example :**__A string is a finite sequence of symbols chosen from some alphabet.__

**(ii) Strings :****01101 is a string from the binary alphabet Summestion = {0,1}**

__Example :__

__The empty string is the string with zero occurrences of symbols. This string denoted e, is a string that may be chosen from any alphabet. Thus |E| = 0.__

**(iii) Empty String :**__The length of a string W, denoted |W| , is the number of symbols composing the string__

**(iv) Length of a string :**__abcd has length 4.__

**Example :**