"Alternative" is an adjective whereas "alternate" is a verb. You use "alternative" when you're presenting possibilites for consideration, like "We could go to the park or as an alternative we could go to a movie". "Alternative" can also be used in a singular context to describe something outside of the norm (e.g. "an alternative lifestyle"), meaning someone that lives in a way that people think is odd. "Alternate" means to vary repeatedly between usually two things. For instance, "Over the last two weeks the weather has alternated between hot and cold".

"Alternate" is not only a verb, but it's also an adjective and a noun too. Check this link for the details: http://www.thefreedictionary.com/alternate Here are 2 useful links explaining the difference between "alternate" and "alternative" and their uses: http://grammar.quickanddirtytips.com/alternate-versus-alternative.aspx http://grandmastales.wordpress.com/2007/02/27/grammar-28-the-hot-difference-between-alternate-and-alternative/