“Den” and “living room”

Question

I was wondering what the difference is between a den and a living room.

What does a den really mean?

For example, an apartment with two Bedrooms, two Baths and one Den:

Answer 1

It is usually meant to be used as a small office in your house. Sometimes it is set down a little lower than the rest of the rooms in the house on the same floor. Most that I have seen do not favor windows, but rather just walls where you can place bookshelves, and if there are windows, they are usually small and placed high for lighting rather than viewing outside.

Here is a picture of Mike Brady's den:

Answer 2

NOAD says a den is a small, comfortable room in a house where a person can pursue an activity in private. Macmillan defines it as a room in a house where someone goes to relax and be alone. In contrast, the living room is an area of the home where the family might convene together.

Usually, in a floor plan, the den is smaller than the living room. Sometimes, the den is not well-suited to be an extra bedroom (as in the floor plan you provided, where the den has no doorway and no closet). Other floor plans are set up where a spare room could be used as either a bedroom or a den (such as the one shown below). In a floor plan like that, a young couple might start off by using such a room as a den, but eventually convert it into a nursery room, when a second bedroom is needed.

Interestingly enough, Macmillian tags that definition of the word as American, which makes me wonder if it's an uncommon term in the UK.