As I said in an earlier post, capitalization can be extremely tricky. We have a tendency to think that the noun is the first part of speech we learn, so it's automatically simple to locate, which isn't true at all (it's true we learn it first--just not true that it is simple!). A noun can become many different parts of speech. (Take the word school--I'm going to school you (verb); The school children (adjective); She is so schoolish when she explains things (adjective); and Let's go to school now (finally, the noun). One cannot truly find the part of speech that a word is out of context. (Be careful of programs that teach parts of speech out of context if you are choosing grammar materials for your children.)
The same thing is true of capitalization--we learn it early yet it is far from simple. Cap this in this instance but not in this. Cap this when it is used as an address but not when it is used in a non-address scenario. And on and on.
Into that madness, enter the proper adjective--another capitalization nightmare, in many cases. Essentially, a proper adjective is a proper noun used as an adjective. The key to using this properly (with the proper capitalization) is knowing for sure that the word is usually a proper noun (without having context, in many cases!).
For example, the following words are capitalized when used as adjectives:
1. Spanish....Spanish speaker
2. Jesuit...Jesuit priests
3. Israeli....Israeli captives
4. French...French braid
More confusing to come tomorrow! Stay tuned to the English blog! (Yes, cap that proper adjective!)