http://en.wikipedia.org/wiki/German_declension#Attributive_adjectives Look at the table for mixed inflection. This is mixed inflection, because of the mein.
Here is a link with a compilation of best explanations and useful comments/replies about adjectives: http://www.mediafire.com/view/h3843u13cx4jleg/adjective_with_Nouns_-_German_from_Duolingo.txt spread this on other comments, do other people a favor :) Good luck learning!
"weiß" with no ending is a predicate adjective only ("Das Hemd ist weiß"). The "e" ending marks too many different gender and case combinations for me to list here. Unfortunately, adjective endings in German are not intuitive and thus not really suited for duolingo's approach. I recommend using a textbook or other website with explicit grammar instruction. That's really the only way to learn them!
There is no need to open up a book to understand the declinsion of German adjectives. It's actually very easy to understand if you follow the three rules that I have listed below. They have yet to fail me. I didn't create them, another user did but I forget her name, sorry. Here is the exact quote:
"Easier way to know adjective endings (my teacher side is coming out)! I have 3 rules for being able to add (or recognize) the correct ending when an adjective precedes the noun.
-Big 3 get an -e (der, die, das) der alte Mann, das kleine Kind, die schöne Frau
-Changin' gets -en (plural and case changes) den alten Mann (accusative), der schönen Frau (dative), die kleinen Kinder (plural)
-No 'the'? Adjective takes over (no 'der' word or just an 'ein') Kaltes Wetter gefällt mir nicht (das Wetter). Ein guter Mann ist schwer zu finden (der Mann).
Now the only tricky part is knowing which 'the' word your noun has :)"
Thanks -- there are indeed algorithms you can learn to determine the adjective endings (I often teach one very similar to yours, based on a flowchart). The problem is, you still have to have a very good grasp on the case system and the genders of nouns. My students struggle with this considerably, and I find that none but the very best are able to use algorithms like this one correctly.
The larger problem is that in actual speech, running through these algorithms in your mind in real time is impossible. The endings simply have to become second nature!
You can't run through the entire delcinsion table in real time either, can you? No matter how you go about figuring out the adjective endings, whether it be through a small list of rules like those that I copied/pasted or through a long declinsion chart, they still have to become second nature for you to use them in real time. So I don't see how that is a problem with his method at all. I see your comments all over talking about how hard this is and how people will have to take a university course to figure it out, but that is simply not true whatsoever. I don't understand why you want to make people think this is so much harder than it actually is. Once you know a few basic rules, it's one of the easiest aspects of German grammar to understand.
This page has helped me a lot with adjective endings, and is really simple to learn without complicated charts to memorize. Take about 10 minutes to read it and I think it will help you too. :)
A great resource for case and gender endings can be found over at: http://www.lsa.umich.edu/german/hmr/grammatik/Basic_Chart.html
As it is not intuitive, it must be memorized.
No. The German system of adjective endings is anything but intuitive to most beginners, and is not really suited to the inductive learning approach (which is what duolingo uses). To learn to use adjective endings correctly, you'll either have to do some serious self-teaching outside of duolingo, or take a university-level course!
I'm not good at this grammar stuff but on another explanative post someone who knew grammar said that in German, with NEUTER nouns it is the -ES ending. I can't remember about the -ER endings and the -EN and the -EM endings, I'll keep checking, one is masculine, one is feminine...etc. EDIT: see Hutcho66 below for a better explanation!
Yeah, sorry, both this explanation and hutcho66's are woefully incomplete. Purchase a good German textbook or look at a website like "about.com" if you want to dive into the complexities of this issue. If you memorize rules like the one above, you'll mess yourself up in the long term.
No, possessive 'adjectives' aren't actually considered adjectives in German, they are articles like der, diese, ein, keine etc. They inflect in the same way as 'ein'. So since Hemd is neuter, it takes (when singular) mein in nominative and accusative, meinem in dative and meiner in genitive.