Ask HN: At what point does a 'website' become an 'application'?

I'm struggling a little with this rather mundane question of terminology: even the simplest of my personal 'websites' are built in Rails. They interact with a database, they are stateful, they are tested. Are they just a 'website', or are they an application?

I ask this from the perspective of discussing the site/app with other people, which is not really something I had done much of before.

What are your thoughts? What terminology should I use to minimize confusion during discussions?