如果你週五用特快專遞寄出這封信，現在應該已經到了。 - Zhictionary

Zhictionary

如果你週五用特快專遞寄出這封信，現在應該已經到了。

If you'd sent the letter by special delivery on Friday, it would've arrived by now.

Source: Tatoeba

Sentence Composition

if
in case
in the event that

you (informal, as opposed to courteous 您 nín)

you (Note: In Taiwan, 妳 is used to address females, but in mainland China, it is not commonly used. Instead, 你 is used to address both males and females.)

to use; to make use of; to employ
(coverb) with; using
to need; to have to (usu. used in the negative or in questions)
usefulness; utility
(bound form) expense; outlay
(courteous) to eat; to drink
(literary) hence; therefore

tèkuàizhuāndì

to mail; to send by post

(pronoun) this; these
(bound form) this; the (followed by a noun)
(bound form) this; these (followed by a classifier) (in this sense, commonly pr. zhèi, esp. in Beijing)

to confer
to grant
to bestow a title
to seal
classifier for sealed objects, esp. letters

letter
mail
to trust
to believe
to profess faith in
truthful
confidence
trust
at will
at random

classifier: 封

now; at present; currently

ought to; should; must

at last
finally
in the end