When I speak with Japanese exchange students they use a lot of "borrowed" words, but we always learn traditional Japanese words in class.
It seems that about 40% of Japanese vocabulary is borrowed.
So, my question is, do you usually use borrowed words all the time, or only in casual speech? Is it considered more professional to use traditional Japanese terms?
I don't, usually, simply because it sounds weird to me, unless they have become part of Japanese already, such as sunglasses, doors, tires, tables, etc. To me, it's a little awkward to see someone using foreign words wrong ways(not languages), not knowing their meanings.
However, since it's getting harder for me to translate English into Japanese, I sometimes mix Japanese with English. Sometimes I can't even find the right word to describe what I want to say (maybe I have lived in the US too long without using Japanese).
日本にはルー大柴という芸能人(コメディアン)が居て、彼は外国語を混ぜた日本語を使う事で有名になりました。しかし、彼は外国語の意味をきちんと理解して使っていないので、彼の文章はとても変な日本語になっています。もちろん彼の外国語の発音もメチャクチャです。
日本人が間違った使い方をしている外国語(英語)に次のようなものがあります。参考にどうぞ。I have been helping my friends learn Japanese in the US for more than 3 years, so it's so easy to find Japanglish.
revenge (they don't really mean to revenge on someone, but this means to play the return games. nothing serious.)
top batter (refers to whoever comes first, even when they are not playing ball games, like the first person to sing at the karaoke parties, etc)
my ball (even when they are referring to someone else's, such as bowling balls or tennis balls. i.e. それってマイボールなの? means "Did you buy those?")
my boom (i.e. 最近のマイブームは読書です, meaning "reading is my new hobby" )
about (i.e. 彼はアバウトな性格です, meaning he is easy going )