The negative short form of the verb to be en anglais : grammaire anglaise / définition

She is not a star ➝ She's not a star. She's not is the short form of she is not.]Use the short form in spoken language and informal situations. Example: she's not Canadian / she isn't Canadian.

Lisa and Sean are not from abroad ➝ Lisa and Sean aren't from abroad. They aren't 
is the short form of they are not. Note: you could also say they're not. Example: they're not from Hawaii / they aren't from Hawaii.

I am not cold ➝ I'm not cold (je n'ai pas froid. Litt. : je ne suis pas). I'm not est la forme contractée de I am not (je ne suis pas). Remarque : Le sujet I (je) n'a qu'une forme contractée. Ex. : I'm not okay with this (je ne suis pas d'accord avec ça).

Shorty isn't the hotel porter, with isn't (short for is not), which is the negative short form of the verb to be that we use for subjects such as he, she and it (Shorty = he). Generally speaking, we use isn't (or 's not) after the name of a person, animal, object or place. Example: the hotel's not in the city centre / the hotel isn't in the city centre.

You could say, for example, they aren't hotel porters, with aren't referring to the subject they, and not to he (= Shorty) as in the original sentence.

The form ’m not follows the subject I , not the name of a person like Shorty. Example: I’m not ready!

They're not American guests (ce ne sont pas des clients américains). They're not est la forme négative contractée de they are not (ils ne sont pas). On peut dire aussi aren't. To be, present simple, negative, short Ex. : they're not Lucy and Mark and they aren't from London (ce n'est pas Lucy et Mark et ils ne sont pas de Londres). 

You can use isn't when the subject is he/she/it or after a name, but not after they. Example: Mr. Obama isn't an Australian guest.

On emploie 'm not (ne suis pas) après I (je), mais pas après they (ils/elles). Ex. : I’m not Irish (je ne suis pas irlandais).

I’m not tired. This is the short negative form that we use after the subject I. Example: I'm not an expert in this field.

You can say she's not happy or he's not Luke, but you cannot use ’s not after the subject I.

’re not follows subjects like we, you or they, not I. Example: we’re not in Bath at the moment.

Caroline isn't the hotel's chef, with isn't , which is the short negative form of the verb to be that you use after the name of a person like Caroline (= she). Note: you could also say Caroline's not the hotel's chef. Example: Magda isn't a kind receptionist / Magda's not a kind receptionist.

I'm not 35 years old is how you tell someone that 35 is not your age using the negative short form of the verb to be To be, present simple, negative, short. Example: I'm young. I'm not 95 years old.

You aren't alone (tu n'es pas seul.e), avec aren't (ou ’re not), forme négative contractée de to be To be, present simple, negative, short que l'on emploie après you (tu/vous). On emploie to be devant un adjectif (ici, alone), pour décrire des personnes, des animaux ou des objets. Ex. : you aren’t tall / you’re not tall (tu n'es pas grand.e).