# Partial word

Jump to navigation
Jump to search

A **partial word** is a string that may contain a number of "do not know" or "do not care" symbols i.e. placeholders in the string where the symbol value is not known or not specified. More formally, a partial word is a partial function where is some finite alphabet. If *u*(*k*) is not defined for some then the unknown element at place *k* in the string is called a "hole". In regular expressions (following the POSIX standard) a hole is represented by the metacharacter ".". For example, *aab.ab.b* is a partial word of length 8 over the alphabet *A* ={*a*,*b*} in which the fourth and seventh characters are holes.^{[1]}