I agree with Ray and Su.Ki. To explain more about the use of the word comfortable, a nurse may ask a patient in the hospital, "Are you comfortable? Do you need more pillows?" The nurse may also ask, "Is the room at a comfortable temperature or are you cold?" Other examples: "These shoes are not comfortable. They squeeze my feet." It would not be proper to use cozy in any of these examples. Examples of sentences with the word cozy: The baby was wrapped in a pink blanket and looked very cozy in her mother's arms. On our date at the coffeehouse, we chose to sit together on a cozy loveseat. (A loveseat is like a couch or sofa but meant for two people instead of three.) It's snowing outside - we should stay inside where it is warm and cozy and watch a movie. I hope this helps!

As Ray says, 'cozy' ( or 'cosy') suggests warmth, but it also suggests 'snugness' and intimacy. For a room to be described as cosy, there are three essential elements : it should feel comfortable, be pleasantly warm and not be too big. In fact, 'cosy' is can often be interpreted as an estate agent's euphemism for 'small'. For example, if a room or home to rent is described as 'cosy', you know that they are trying to make a description of any undersized property sound positive!

It's pretty much the same, but cozy is always associated with the feeling of warmth. For example, I could say that my bed is nice and cozy during the winter.

Sometimes, (in America at least) people will abbreviate "comfortable" to "comfy". "This is my favorite/favourite shirt because its so comfy." "This couch isn't very comfy. It's hard as a rock."