I found that the room where people sit (normally in the entrance of the house or in the center of the house) is named in English by one of the following three names:
1) sitting room
2) living room
3) lounge room
My question is which one of them is more common in the British English and which one of them is more common in Am English - or all of them are used equal in British and American English?
I have never heard "lounge room" in American English.
"Living Room" is common. "Sitting room" is less common, and is more formal and somewhat antiquated - something you'd read in a 19th century book.
See this ngram of the American English corpus.
"Family room" is also used in AmE, and indicates a less-formal room.
Growing up in the South, the older people called it "the parlor". From the 1950s on at least, it was called the "front room". Gradually people began calling it the "living room", possibly influenced by television. A "lounge" was the anteroom to a public restroom, usually containing a chaise longue. This is just personal experience of U.S. Southern usage.
I'm an Australian, so speak British English. To me, a lounge or lounge room, less commonly called a sitting room, is a room containing a lounge suite (set of soft/comfy furniture) where one quietly relaxes with a companion, knitting or crochet, a book, or TV, and on more formal occasions invites guests to relax and socialise with us. If there is a fireplace in the room it would be used often during cold weather, especially in the evenings, less often and usually only on more formal occasions during warm/hot times of year. A living room is a multi-purpose, communal room. It's where friends chat around a table, eat snacks or meals, the children play, and the more noisy activities occur. We live in a very small house so the living room is the main room in the house, where we cook, eat, talk, socialise, read, use as an office and computer room, do crafts, and most everything else except sleep or wash. That said, names given for the main rooms in a house are not set in stone. They will depend on the number of rooms available in the house for various activities. And families will tend to use whatever room names have been traditionally used in their family group.
Lounge room is Australian English. Growing up in the UK, we just called it the lounge, but when I moved to Australia everyone called it the lounge room. In Australia, when you say 'the lounge', you're usually referring to the sofa and other lounge room furniture. So you go into the lounge room and sit on the lounge.
Sitting room = British English and still used today.
Living room = American English
Lounge = not a living room. It's what might also be called a TV room. Lounge room sounds like an institution. Not a single-family house.
In Britain it is to a large extent governed by social class.
If you are really posh you might call it the drawing room. That has nothing to do with pencil and easel, but it is the room to which one withdraws e.g after dinner.
Lounge is widely used in Britain but perhaps its popularity is relatively recent i.e. since WW2.
Sitting room is still widely used mostly by the polite classes.
The working class term is living room, which is where people do everything - eat, relax, and watch TV. As houses have become larger and people wealthier many have a dining room and a lounge. In houses where they are combined as one - estate agents are apt to call it a lounge-diner.
The parlour which someone said was popular in the American south is very dated in Britain - and was used in houses like Downton Abbey - peopled by the gentry classes.
From the Victorian to the immediate post-WW2 period, lower-middle class homes in Britain often still had what was known as a front-room. This was the best-kept room in the house, the one at the front facing the street. It was used by the family for receiving important guests e.g the vicar, the doctor etc. and on high-days and holidays - such as at Christmas. Families would still continue the Victorian practice of putting an atractive plant by the front window - such as an aspidistra.
This practice was believed by George Orwell to have been emblematic of the determination of that class of British people to present a respectable face to the world - and is central to his 1936 novel Keep the Aspidistra Flying.
In more recent decades Britain's transformation from manufacturing to service economy has changed the social class system, and millions of the industrial terraces which would have sported aspidistras in their "front-rooms" have been demolished. However in parts of inner London, the small terraced houses themselves are alive and well, and have become bijou residences which change hands often for in excess of a million pounds. But families use the houses ergonomically - and the aspidistra is dead.
