Q.
I can't hear the "u" sound of
the word "desu." Is it supposed to be pronounced?
A. Japanese
syllables are written with a vowel (a, i, u, e, o) or a combination of a
consonant and a vowel (ka, sa, ta etc.). The only consonant that stands by
itself is "n". For example: "kirin (ki-ri-n)" as in
"giraffe". Therefore, "desu" is pronounced as "de-su"
with two syllables. Since the last "u" is a very subtle sound and
tends to be whispered, you might not be able to hear it. It is not necessary to
emphasize it. I think it is best to listen to a native speaker closely and mimic
what you hear.

