Do some adjectives not inflect?
So, I'm currently not to the adjectives section on Duolingo, but I'm trying to understand the grammar of adjectives before I get there.
Adjectives like vit, -itt, -ita inflect with common/neuter, definiteness and with number, e.g. ett vitt äpple, en vit varg, vita vargar, de vita vargar.
However some adjectives, from what I see, do not inflect at all, e.g. ett lila äpple, en lila varg, en lila vargar.
Am I incorrect, or missing something?
You're right, many adjectives do not change. lila 'purple' and gyllene 'golden' are two colors that don't. Two colors that don't inflect, or do so with great difficulty, are beige and orange, Swedes struggle with these since they don't fit in our system.
Carnaedy gave a few examples in this comment, she wrote:
Actually, a huge part of adjectives that end in -a, -e or -s in their dictionary (-en) form are not declined whatsoever, e.g., annorlunda, bra, udda, äkta, leende, spännande, öde, gratis, gammaldags, etc. There are exceptions though, it is not an absolute rule.
A very common word, kul 'fun', doesn't inflect at all, and is pretty awkward to use in the plural (personally, I avoid saying stuff like dom är kul). It's been in use since the 19th century, so it's pretty interesting how it still hasn't been fitted into the inflection system, given it's similarity to ful.