You use truly to emphasize that something has all the features or qualities of a particular thing, or is the case to the fullest possible extent.
a truly democratic system.
一个真正民主的体制。
Not all doctors truly understand the reproductive cycle.
并非所有的医生都完全地了解生育周期。
You can use truly in order to emphasize your description of something.
a truly splendid man.
一个非常好的男人。
You use truly to emphasize that feelings are genuine and sincere.
Believe me, Susan, I am truly sorry.
相信我,苏珊,我由衷地感到愧疚。
Yours truly
You write Yours truly at the end of a formal letter, and before signing your name, to someone you do not know very well.
Yours truly, Phil Turner.
菲尔·特纳敬上。