I need an adjective for that please, is about the energy of the room feeling both sad but quiet and peaceful.
- There was a ____ atmosphere in the room.
I need an adjective for that please, is about the energy of the room feeling both sad but quiet and peaceful.
Try sombre (US somber).
serious, sad, and without humour or entertainment:
a sombre atmosphere/voice/face
The funeral was a sombre occasion.
[Cambridge]
Perhaps the closest you'll get is melancholic:
melancholy [noun]:
a feeling of pensive sadness
- an air of melancholy surrounded him
[also adjective]
Oxford Dictionary of English, courtesy of Google
'Pensive' must imply peacefulness:
pensive: 1. thinking in a quiet way
Earlier responses are good, however "sad but quiet and peaceful" suggests an accepted sadness, and previous answers didn't convey that to me. Some other options might be:
You can also use a word that does not have a definition related at all to what you need, but which conveys the right sense:
And so on.
Also, to address other responses with my (subjective) opinion:
Elegiac may suit your needs. According to the OED, elegiac means:
Of the nature of an elegy; of or relating to elegies. Hence: mournful, melancholy, plaintive.
https://www.oed.com/dictionary/elegiac_adj?tab=meaning_and_use#5838885
Elegy, in turn, means:
A song or poem of lamentation, esp. for the dead.
https://www.oed.com/dictionary/elegy_n?tab=meaning_and_use#5628297
Since songs and poems of lamentation for the dead are usually grave and solemn, an "elegiac" atmosphere should be one that is not only sad but peaceful as well. The peace here, however, may be understood to be thrust upon the atmosphere, a sense that the nature of elegies evokse. As such, if you are seeking a word that expresses peace of mind, elegiac may not be appropriate. But if you are looking for a word that conveys an imposed peace, elegiac will do.
Perhaps forlorn? While there can be an additional layer of pity understood with that one, it conveys a solitary (which some may equate with peace) sadness.
I'd suggest triste. M-W says mournful.
(The editor thinks it's too brief without the link.)
I believe my answer is exactly what you are looking for: Bittersweet
https://www.oxfordlearnersdictionaries.com/definition/american_english/bittersweet
They were bittersweet memories.
As others have said in their answers and comments, you may not find a single word that denotes exactly what you want, so you'll have to decide what connotations you want to emphasize. With that in mind, here's another non-literal option: resigned.
Definition of "resigned" on Wiktionary:
Characterized by resignation or acceptance.
You didn't say why the people in the room feel the way they do. If they are disappointed but choose to react with acceptance rather than defiance, "resigned" could correctly describe their mood.
Perhaps the word 'nostalgic' may be useful. It conveys (to me at least) a little sadness and some peacefulness.
Unfortunately it also carries the meaning of memory, yearning, and so on, not part of your request. But maybe. :-)
There was a dead atmosphere in the room.
(No, I'm not going to explain what dead means, if you must have an explanation go look at the definition of dead on Wiktionary.)
And if the notion of a dead atmosphere isn't making you sad enough, think of a dead kitten - sad and peaceful enough for anyone, surely?