I've been using vi for over 25 years... my fingers themselves just "think" vi. In all those years, I have never had the need to have vi tell me the length of a "word". Rather, I tell vi to do something to a word, and even define what words are.
In vi (not vim), determinging the length of a word would require using external commands, where a word could be used as input to wc -l
In vim (which you think of as vi), there is an entire programming language. This is an area I'm not well experienced, and have had little need, so I can't help you here. This would be a good question for the vim.org mailing lists.
If you are serious about becoming a "master", spend some time learning how to perform shell escapes using editor content as input. Hint: try each of the following lines while editing some test file - see if you can tell what they are doing. Hit Enter after each command you try, and u