How do I search for words that occur twice consecutively?

You can use one of the following search commands to locate words that occur twice consecutively:

     /\(\<\w\+\)\_s\+\1\>

     /\(\<\k\+\)\_s\+\1\>

The main difference is the use of ‘\w’ and ‘\k’, where the latter is based on the ‘iskeyword’ option which may include accented and other language specific characters.