The word less is of course pronounced les, but it can also be a suffix. In this case it is unstressed and pronounced ləs or lɪs, the former being much more common than the latter these days. Here are some examples:
careless = ˈkeələs
expressionless = ɪkˈspreʃnləs
motionless = ˈməʊʃnləs
powerless = ˈpaʊələs
valueless = ˈvæljuləs
As you can see from the above, this suffix is stress-neutral. This means the position of the main stress is not affected when the suffix is added to a word.
Updated 2013_11_03 With thanks to Alex Rotatori for a suggestion.