Register – choosing appropriate language for the situation

a letter to a business associate who you do not know very well

an e-mail to a colleague who you see every day at work

a covering letter

a report

a professional e-mail

a letter of complaint

an e-mail to a business associate you know very well

use more active structures

use “I” or “You” as the subject of a sentence

use contractions (I’ve just got your e-mail)

use longer, more complex sentences

use abbreviations such as BTW, FYI, etc.

have less informal phrasal verbs

use CAPITAL LETTERS, exclamation marks! and emoticons 😉