Question

[tidal tundra]

À

Can someone tell my why she used aux there

cheveux is not a plural I think

[sonic solar]

À notes the characteristic of a person or an object. Here, blond hair is a component of the woman.
Aux = à+les because the blond hair is specified. Un cheveu is a strand of hair, as such it can be counted.

[tidal tundra]

Oh

Thank you i didn’t know

[tidal tundra]

Every time that’s the case we use Aux?

[sonic solar]

When something is specified? Depending on what it is, the article au changes.
Un homme au manteau blanc
Une femme à la robe longue
Un collègue à l'oreille coupée
Un enfant aux cheveux blonds

[tidal tundra]

But the depending on what it is what does it really depend on

Are there rules

Does it depend on the person of the characteristic

Whether it’s a guy or girl

Because for un homme you said au

And une femme you said à la

[sonic solar]

That's irrelevant because you can also have "une femme au manteau blanc" and "un homme à la robe longue".

It only depends on the gender and number of the component in question.

Manteau is masculine singular so you use au, robe is feminine singular so you use à la.

[tidal tundra]

How about the last one

Enfant means child

So aux ?

[sonic solar]

Cheveux is masculine plural so aux is used. Enfant has nothing to do with the agreement.

À only serves to connect a specified characteristic to the person or thing. Since there is something specified, a definite article is used and agrees in gender and number with said characteristic and can be combined with à when possible (à+le = au, à+les = aux).

Un homme à + characteristic
Let's say the characteristic is manteau blanc. Since it's a specified element, we add the definite article which is le because manteau is masculine singular: le manteau blanc.
We combine it with "un homme à": un homme à + le manteau blanc
We then combine à and le because it's a mandatory contraction: un homme au manteau blanc.

Whataver comes before à never even comes into the agreement equation.

[tidal tundra]

Ohh

[tidal tundra]

I get you

That make way more sense

Tysm

I appreciate it