The verb 'to be' is an exception. It is the most irregular verb in English and has its own rules for the Negative and Question form.
Positive
| I | am | happy. |
| He/She/It | is | |
|
We/You/They |
are |
Positive - Contracted Form
| I | 'm | from Italy. |
| He/She/It | 's | |
|
We/You/They |
're |
Negative
| I | am not | 23 years old. |
| He/She/It | is not | |
|
We/You/They |
are not |
Negative - Contracted Form
| I | 'm not | sad. |
| He/She/It | isn't | |
|
We/You/They |
aren't |
Question Form
For the creation of the question form we invert the verb and the subject.
| Am | I | Russian? |
| Is | He/She/It | |
| Are | We/You/They |
Short Answers
Yes, I am. (not Yes, I'm)
Yes, you are. (not Yes, you're)
Yes, he/she/it is (not Yes, he/she/it's)
Yes, we are (not Yes, we're)
Yes, they are (not Yes, they're)
No, I am not. or No I'm not.
No, you are not or No, you're not or No, you aren't
No, he/she/it is not or No he/she/it's not. or No, he/she/it isn't.
No, we are not.or No, we're not. or No, we aren't.
No, they are not. or No, they're not. or No, they aren't.