metablue wrote:I mean, what kind of grammatical entity is "yoroshiku"?
"Yoroshiku" is an adverb. "Yoroshii" is an honorific Japanese adjective meaning "good". So "yoroshiku" means "well". That's why Peter always translates "Yoroshiku onegai shimasu" as "Please be nice to me" or "Please treat me well"
I've been thinking of "desu" as "is". But in this case it obviously isn't an "is" in the sense that I understand "is". So I have to reformulate my concept of "desu". I understand that desu makes things politer, but I thought that it was just a more polite version of "is", so you couldn't use it anywhere that an "is" doesn't make sense
Although "desu" is the Japanese copula, equivalent to the English "to be", it is often used simply to make a sentence more polite with no other meaning whatsoever.
What kinds of grammatical structures can you attach a "desu" to?
You can add a "desu" to the end of just about anything.
For example, to say in plain Japanese, "I didn't understand", you say "wakaranakatta." This is past tense. You can make it more polite by adding "desu". It seems like a silly thing to do, because "wakaranakatta" is past tense, and "desu" is present tense, but it just makes the sentence more polite. "wakaranakatta desu" is perfectly acceptable Japanese. (The even more polite form is "wakarimasen deshita".)