Thesaurus search free thesaurus' all around the world. A thesaurus will find words that are spelled differently.
An example: search for their and you will get there, and they're
Wildcard characters let you search for words when you
don't know all the letters in them -- for example, if you're
not sure how to spell a word. Webster's Dictionary and
Thesaurus lets you use the standard wildcards "?" and "*"
to help in such situations.