...from Zen and the Art of Motorcycle Maintenance, strictly for the purpose of generating a conversation here, should anyone care to take part:
What is quality?
My short answer is: a measurement. I don't really have a long answer yet.
fitness for the intended purpose
A quality couch is comfortable and reasonably esthetic and stays that way.
A quality car gets you there. Or impresses the girls or whatever is the reason you bought it.
Quantity is a measurement. Quality is that which is measured. Sometimes "quality" is used to mean 'having a large quantity of some desirable quality'.
My best painter friend would, when a painting struck him as extremely beautiful, exclaime in admiration: "Oh, my goodness, the quality of the light!...."
How would you qualify this quality?
A quality is a distinctive feature or property of something, (or a trait of somebody). It can be good or bad, though by itself it leans more to the positive side of the spectrum.
Ok, I shall bite (being aware that pertinent answers have already been given).
In my youth, I tacitly assumed that "quality" meant good quality (of any material or immaterial thing), i.e. the word implied a positive value judgment. Later, at work, we had to attend a course in "quality control", and we learned that this means to assure that a product corresponds to specifications, i.e. that it be neither worse nor better than specified (if it were better, this would mean a free gift to the customer). This was quite a change in outlook for me!
the quality of the light!...."
How would you qualify this quality?
I always 'look for the light' when viewing a landscape or still life. In this case I would suggest that the quality would refer to the artists rendition of 'the light'.
Yes, that is why I chose the word condition, because it was a special condition of this rendition that made him exclaim like this. Which might correspond with what sieber wrote "product corresponds to (the condition of) specifications". In my friend's case it was positive, but just another intonation and it would be negative. Quality not having any measurement of value in itself.
The term "taste" once only meant good taste; the concept of "bad taste" came later.