Informal English includes conversational language. Contractions such as can't, won't, and I'm. Contractions are not used in formal English. Formal English is carefully worded as in academic or professional writing. Word choice is important in formal English.

For example, in formal English one would use the word whom instead of the word who in certain situations:

Formal English: With whom did you study?
Informal English: Who did you study with?

Formal English: Did you go to the store?
Informal English: Go to the store?

Formal English: Did you finish the assignment that the professor posted?
Informal English: Did you finish the assignment the professor posted?

APOLOGIZING

Formal

<em>- We would like to apologize for any inconvenience caused.</em>
<em>- Please accept our apologies for the delay.</em>
<em>- Please let us know what we can do to compensate you for the damages caused.</em>
<em>- We will make sure that this will not happen again in the  future.
- I am afraid I will not be able to attend the conference.
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Informal

<em>- I’m sorry for the trouble I caused.</em>
<em>- I apologize for the delay.</em>
<em>- I promise it won’t happen again.
- I’m sorry, but I can’t make it to the meeting.</em>

<ul> <li><em>General greetings (Formal)</em><ol> <li>Hello!</li> <li>How are you?</li> <li>How are you doing?</li> <li>How is everything?</li> <li>How’s everything going?</li> <li>How have you been keeping?</li> <li>I trust that everything is well.</li> </ol>

<em>General greetings (Informal)</em>

<ol> <li>Hi.</li> <li>What’s up?</li> <li>Good to see you.</li> <li>How are things (with you)?</li> <li>How’s it going?</li> <li>How’s life been treating you?</li> </ol>

<em>Greeting a person you haven’t seen for a long time (Formal)</em>

<ol> <li>It has been a long time.</li> <li>It’s been too long.</li> <li>What have you been up to all these years?</li> <li>It’s always a pleasure to see you.</li> <li>How long has it been?</li> <li>I’m so happy to see you again.</li> </ol>

<em>Greeting a person you haven’t seen for a long time (Informal)</em>

<ul> <li>How come I never see you?</li> <li>It’s been such a long time.</li> <li>Long time no see.</li> <li>Where have you been hiding?</li> <li>It’s been ages since we last met.</li> </ul> </li> </ul>