Is there any way to edit a keyword already entered

Question

Lets say I accidentally spelled a keyword two ways, but I wanted to convert all instances of version a to version b, so I eliminate a and keep b.  Or I just changed my mind about a keyword and want to change it wherever I have used it.  But I have applied these keywords to multiple images in multiple folders. 
Is there any way to do this other than eliminating all of either a or b and re-applying one by one?  This would be extremely tedious; nigh impossible. 
I used Bridge for a while previously and am gearing up to try to tag all  my photos, and as I recall this was a major problem for me.  

Answer 1

You can search for the incorrect keyword, find and change, but as you admited it is a slow process.
I would like to disagree with this
You can use the find command for both keywords with Source set to main folder including subfolders and non indexed files. Use the plus sign to add the second keyword and this should provide you the files with both keywords in the content window (it may take a while depending on amount of files and folders and if your files have been indexed before or not)
When the result s there use the filter panel to sort only files with the first wrong keyword, select all files and then change the keyword. You can do so in the keyword field of the metadata tab but better would be to use the keyword panel. First add the new correct keyword to the list and then select the wrong keyword and click on the checkmark to remove the keyword from the selected files.
Then with right mouse click menu delete the first wrong keyword from the list and click on the correct keyword you want to add to the already selected files.
Repeat this for the files with the other wrong keyword and you are done