In my reading (especially in Japanese dictionary definitions) I sometimes come across combinations of simple kanji whose meanings I understand perfectly but whose readings I don't know. For example, I have come across 右上 several times, and though the meaning is obvious, I cannot find it in a dictionary. Is it みぎうえ or じょうゆう or what? Do Japanese people even care about the readings of these kinds of words or do they just read them like symbols? I know it doesn't really matter. I know I'll probably never use these kinds of words in conversation -- I'm just curious.

Everyone has that problem, including native speakers. For more common words, native speakers don't have to worry because they know what is a word and what isn't. For rarer words they probably just don't care, guess at a reading, and move on.

(I would read 右上 as みぎうえ, personally.)

http://jisho.org/words?jap=%E5%8F%B3%E4%...dict=edict

みぎうえ it is.

kusterdu Wrote:For example, I have come across 右上 several times, and though the meaning is obvious, I cannot find it in a dictionary. Is it みぎうえ or じょうゆう or what?

I assume that it's because most people would think of that as being two words instead of one. Sort of like how you typically won't find "upper right" in a dictionary.

Though Rikaichan knows it

I actually came across this word and the whole other set （左下 etc.) a few days ago, whilst playing through the new fire emblem on the ds.

kusterdu Wrote:For example, I have come across 右上 several times, and though the meaning is obvious, I cannot find it in a dictionary.

Omg. At first I confused the first part with the kanji for "stone" (Heisig keyword), so I thought, hmm it must mean "meteorit" (stone from above) I was dead wrong

kusterdu Wrote:In my reading (especially in Japanese dictionary definitions) I sometimes come across combinations of simple kanji whose meanings I understand perfectly but whose readings I don't know. For example, I have come across 右上 several times, and though the meaning is obvious, I cannot find it in a dictionary. Is it みぎうえ or じょうゆう or what? Do Japanese people even care about the readings of these kinds of words or do they just read them like symbols? I know it doesn't really matter. I know I'll probably never use these kinds of words in conversation -- I'm just curious.

「右上」は「みぎあがり」なんじゃないの？

You just read it in a manner that would get the meaning across the most efficiently.

Even if you've read a word incorrectly, Japanese speakers would know what you meant. Such as 間 (あいだ/ま/かん):

この間はありがとうございました。
間に合わなかった!
1週間間の休暇ですが...。