The Beam is a Home Theatre device you can pair surround speakers (only as a same model pair pair), plus a sub to it as one room.  .  You can set persistent groups too.

The rule for non Home Theatre products is one speaker (or a stereo pair) per room plus a Sub.

A Sonos ‘Room’ can be several things (either with, or without, a Sub):

• A stand-alone speaker 
• Two speakers ‘stereo’ paired
• A Home Theatre player with bonded surrounds

So, just as examples, a user could have a Home Theatre bonded setup called ‘Living Room TV’ and a pair of speakers in the same room called ‘Living Room HiFi’. The naming conventions are entirely upto the user.

Theres no benefit in having two ‘rooms’ with the same name, as it will likely confuse things and create uncertainty as to which speakers are being selected for playback.

There are of course overarching ‘Groups’ available to the user aswell in the Sonos App - See ‘Settings/System/Groups’ where Sonos ‘Rooms’, like ‘Living Room TV’ and ‘Living Room HiFi’ can be combined and simply given a group name of ‘Living Room’.

There are many possibilities for the user to choose from, using the features available in the App, it’s perhaps a case of understanding what’s available and how you would like to perhaps use those features.

The App will cater for most things, but I would suggest maybe keeping ‘Room’ and ‘Group’ names unique where possible to keep things simple and easily identifiable.

Perhaps you can kind of guess, but I think there are two main reasons why Sonos has restrictions on devices that can be bonded into a single room.  Primarily, I think it’s because the ability to stereo pair speakers, and bond speakers in a home theatre, but it has technical limits.  They have not setup the ability to use a Sonos One as a center channel speaker for example, so it’s simply not allowed as part of a room.  Speakers are not just randomly placed in a room in the Sonos app, they are there with a specific purpose.  There is also trueplay tuning.

So sure, a customer could possibly understand the limits, but still want speakers placed in the same room together and playing in sync.   You have your port and Beam in the same room.  Sonos has a need to keep things simple and easy to understand for everyone.  They don’t want people putting odd combinations in a room and having it sound terrible.   They don’t want people thinking that if they just put a speaker in front of the TV and add it to the existing room, they have a center channel speaker now.

It doesn’t help that the concept of a room works differently in Google Home for example.

This does all help make more sense of the "Room” paradigm in Sonos. What still confuses me though is that I have the Port and the Beam in my living, and when I play cd's (or vinyl) through the Port, it produces audio over the Beam. So for that purpose, they function as a single unit, which made me believe they should be assigned to a single room.

Btw, I hadn't realized yet that Sonos limits what's possible in a room. I suppose if I want to expand the audio in my living beyond the Beam (and associated devices), I'd have to create an extra room for the extra speakers, and group those rooms? (It's a rather large room, and the Beam is in the front half, so I may in the future want one or two Ones in the back half.)

The Port produces audio over the Beam because you’ve assigned it to, not because it is in the same room. They still function as separate rooms.

You can either add two One (SL)’s as (surrounds to a Beam (then they’re in the same room) or set up a separate room and group them (two rooms). You can only add two surrounds (or one Amp as surround) to a room.

Okay, that's cleared everything up. Still feel it would make more sense to call this feature a “Set” or “Unit” instead of a “Room", but at least now I get it :-)

I do wonder what to call my living “Room” now. The Beam, which I use for home cinema but also to play music in the living, is one “Room”; the Port is a second “Room” physically located in the living. I think I'll go with your suggestion, @Ken_Griffiths, and call them “Living room TV” and “Living room HiFi", respectively.

My Connect is called “Connect CD player” for this reason.

You do need to remember Sonos was one of the first to use the concept of a "Room”, when a room was only one device (not even a speaker) - from 2006.

Sonos used to refer to call them ‘zones’, and I wish they had stuck with that.  However, people think of homes as filled with different rooms, not zones, so I can understand the logic.  “Set” in Sonos language is a bundle of speaker packages they sell on this website, and often contain speakers that you can’t setup as the same rooom.  It’s already used for marketing, in other words. “Unit”….immature people like me will just giggle.  “My unit is broken!”

Agreed.  When location alone doesn’t work, then next level is function.  For my family room, I use “Family Room” and “Main TV”.

I would like to see Sonos come up with some sort of advanced level configuration for cases like this though.  If you have a situation where 99% of the time you want 2 rooms to be grouped together, for example.  Or perhaps where you have two Sonos rooms in a physical room, one of the rooms should always play TV audio and the other to always play streaming audio.  I do see a couple problems with this though.  One is that it would add complication to integration with third party smart home devices and apps.  The other is that, as Sonos features expand, it would mean certain advanced settings wouldn’t make sense anymore.

@melvimbe You're right. I forgot that (it was way before I could buy Sonos devices).

This is a neverending discussion (though fun to think about). In Philips Hue you have “Rooms” and “Zones". Zones can be parts of rooms, or even (I believe) contain parts of different rooms.

Since the room name is just a label, you could refer to one “speaker set” as “Beam” and the other as “Port”. Indeed, there’s nothing (other than common sense?) stopping you from identifying the Beam and any associated speakers as a room called Port, and the Port as a room called Playbar.

One thing that confused me initially is that the Sonos app itself suggests names of physical, identifiable house rooms for the Sonos “Rooms”, and creates numbered duplicates when a device cannot be added to a ‘room’ that's already in use. So the Sonos app itself gives off a strong signal that Sonos “Rooms” correspond to real-life rooms.

For my smart central heating system, rooms correspond to physical rooms, with one or more radiators and a single temperature control. And in that context, zones are groupings of rooms (in my case, a single zone for the entire house).

I propose the term “Combo” for Sonos “Rooms". 

I think I'll proceed to call my “Rooms” Bert, Ernie, Count, and Bigbird.

That will work too. Does everyone in your household know which is which? 

I'm currently the only one who knows how it works, or who has the app. POWER! UNLIMITED POWER!

I have mostly room names except for the lone: End Table Play 5.

I do have a One named CR_2 that I use as a play/pause button on the Computer Room Beam setup.

You can do custom room names and have several Sonos all under the same name, just with a trailing number.