'Three' is on the list of stop words. The fix is here:
https://dev.mysql.com/doc/refman/5.6/en/fulltext-stopwords.html
A work around for sites you don't own is to use DDG : search for third site:2ndbook.org
Edit History
'Three' is on the list of stop words. The fix is here:
https://dev.mysql.com/doc/refman/5.6/en/fulltext-stopwords.html