Learn Hardcore French: Marie veut rencontrer des voisins qui soient prêts à parler lentement avec elle. - Marie wants to meet neighbors who are ready to speak slowly with her.

Soient is the present subjunctive of être. It is used because the sentence expresses a wish about some people who are not specifically identified yet.

With an indefinite / unknown group you are hoping to find, French often uses the subjunctive in a relative clause introduced by qui:
- Marie veut rencontrer des voisins qui soient prêts…

This suggests:

She does not yet know who these neighbors are, or even if they exist.
She is expressing a wish or requirement about the kind of neighbors she hopes to meet.

If you said:

Marie veut rencontrer des voisins qui sont prêts à parler lentement avec elle.

this would sound more like:

There are already known or existing neighbors who are ready to speak slowly, and she wants to meet those particular neighbors.

So:

qui soient → desired / hypothetical people
qui sont → known / identified, or at least presented as factually existing

Is the subjunctive always required after qui?

No. Qui itself does not automatically require the subjunctive. What matters is the meaning of the whole sentence, especially:

Are we talking about something definite, known, and real?
Or about something hypothetical, desired, or not yet known to exist?

Rough guide:

Indicative (e.g. sont) after qui when:
- The antecedent is specific and known:
  - Je connais des voisins qui sont très gentils.
    (I actually know them; they exist.)
Subjunctive (e.g. soient) after qui when:
- The antecedent is indefinite, hypothetical, or just wished for:
  - Je cherche des voisins qui soient très gentils.
    (I am looking for such neighbors; I don’t know if I’ll find any.)

In your sentence, des voisins are not identified; Marie just wants to find that kind of neighbor, so French favors qui soient.

Why is it des voisins and not les voisins?

Des voisins means some neighbors, in a general, non‑specific sense. Marie is not thinking of particular neighbors she already knows.

des voisins = some neighbors, any neighbors, neighbors in general
les voisins = the neighbors, a specific group already identified in context

Compare:

Marie veut rencontrer des voisins qui soient prêts…
She wants to meet some neighbors who would be willing…
Marie veut rencontrer les voisins qui sont prêts…
She wants to meet the neighbors who are ready… (we already know which ones, at least in context)

Using des helps keep the idea that these neighbors are as yet unknown and non‑specific, which matches the use of the subjunctive soient.

Why does prêts have an -s at the end?

Prêts is an adjective that must agree in gender and number with the noun it describes.

Noun: des voisins → masculine plural
Adjective: prêt (masculine singular) → becomes prêts (masculine plural) to match.

Basic patterns for prêt:

Masculine singular: prêt
Feminine singular: prête
Masculine plural: prêts
Feminine plural: prêtes

Since voisins is masculine plural, you need prêts.

Marie is a woman. Why isn’t it prête instead of prêts?

The adjective prêts is not describing Marie; it is describing des voisins.

Subject of the relative clause: qui = des voisins
So the agreement is:
- des voisins → masculine plural
- prêts → masculine plural form of the adjective

If the adjective were describing Marie, it would indeed be prête:

Marie est prête à parler lentement.

Why is it rencontrer des voisins and not rencontrer avec des voisins like to meet with in English?

In French, rencontrer quelqu’un already means to meet someone or to run into someone. You do not normally add avec after rencontrer.

Correct:
- Marie veut rencontrer des voisins.
Incorrect / unnatural:
- Marie veut rencontrer avec des voisins.

French structures:

rencontrer quelqu’un = to meet someone
avoir une réunion avec quelqu’un / se réunir avec quelqu’un = to have a meeting with someone

So the natural French translation of to meet some neighbors is simply rencontrer des voisins.

What is the difference between rencontrer, retrouver, and se rencontrer?

These three verbs all involve meeting, but they are used differently:

rencontrer quelqu’un
- To meet someone (either planned or by chance), from one person’s point of view.
- J’ai rencontré mon voisin dans la rue.
retrouver quelqu’un
- To meet someone again, to meet up with someone you already know, usually by arrangement.
- Je retrouve mes amis au café à 18 h.
  (I’m meeting up with my friends at the café at 6 p.m.)
se rencontrer
- Reflexive form, focusing on the mutual idea: people meet each other.
- Nous nous sommes rencontrés à l’université.
  (We met each other at university.)

In your sentence, rencontrer des voisins is appropriate because Marie wants to meet (get to know) some neighbors.

Why is it parler lentement and not parler doucement?

Both can be translated as to speak slowly/softly, but they focus on different aspects:

lentement = slowly in terms of speed
- parler lentement = speak at a slow pace, take your time between words.
doucement = gently / softly in terms of tone, volume, or manner
- parler doucement = speak in a soft or gentle voice (not loud or harsh).

In the context of helping Marie understand French better, the key point is speed, so parler lentement is the most natural choice.

Could we say lui parler lentement instead of parler lentement avec elle?

Yes, lui parler lentement is perfectly correct and actually more natural and concise in many contexts:

parler lentement avec elle = speak slowly with her
lui parler lentement = speak slowly to her

Both are understandable. Differences:

lui parler lentement:
- More typical French phrasing.
- Uses the indirect object pronoun lui instead of avec elle.
parler lentement avec elle:
- Slightly more literal or emphatic on being with her / in her company.
- Still correct but a bit heavier in style.

For everyday speech, many natives would say:

Marie veut rencontrer des voisins qui soient prêts à lui parler lentement.

Is the word order parler lentement avec elle fixed? Could it be parler avec elle lentement?

Both orders are grammatically possible, but parler lentement avec elle sounds more natural here.

Usual pattern: verb + adverb (how?) + complement (with whom?):
- parler lentement avec elle
Alternative: verb + complement + adverb:
- parler avec elle lentement

The second option would be understood, but French tends to place simple adverbs like lentement right after the verb when possible. So:

Prefer: parler lentement avec elle
Avoid in formal style: parler avec elle lentement, unless you want to give a special emphasis to avec elle.