My team uses MadCap search for our help site, and we've had persistent issues with searches that include the word "not." After a fair bit of testing, we've figured a number of things out:
- When written as "not" or "NOT" the word functions as a Boolean operator.
- When written as "Not," "nOt," etc. it's searched like a normal word.
- The function of this operator is to search for things before "not" but not after it. E.g., searching "Can not log in" returns pages that contain "can" and don't contain "log" or "in."
- If you start a search with "not" it fails with an error. E.g., "Not able to log in" throws the error "Ensure that the search string is properly formatted."
- "not" is on the stopwords list by default, but that doesn't effect the Boolean functionality. Likewise adding "not" to synonyms appears to do nothing.