why use "tous" not "toutes" (it is all women celebrating)

Question

nous allons tous fêter ça

Accepted Answer

Hi Kathleen,
In fact there are two sentences in the text -
Je suis tellement heureuse pour nous toutes= I am so happy for all of us (women who got the pay rise)
And the last sentence -
Nous allons tous fêter ça= We are all going to celebrate this 
Meaning all of us, an indeterminate number of men and women, not restricted to just women.
Hope this sheds light on the difference.

Answer

Hi Kathleen,

Tout in all its forms can be very tricky. It can function as:

an adjective, an adverb, a noun or a pronoun. Here it is being used as a pronoun (invariable) .

e.g. Nous tous - all of us, vous tous - alla of you, ils/elles tous - all of them.

It is made even more difficult to recognise since the two pronouns are separated (allowed).

Hope this helps,

Tom