FR: le train qui part à 10 heures - pronom relatif

[queenkatherine__]

nous prenons le train qui part à 10 heures.
qui replaces a subject.
que replaces a direct object.
In the sentence above, the direct object is the train, right? And we refer to the train (that leaves at 10 o’clock) so why is qui used? What am I missing?

 

[Yendred]

"qui" indeed replaces the subject in the expression "qui part à 10 heures".
"le train" is the implied subject of the verb "part":
le train part à 10 heures

Compare with:
Nous présentons le ticket que le contrôleur demande.
Here "que" replaces the direct object of the verb "demande":
le contrôleur demande le ticket.

 

[OLN]

"le train" is indeed the direct object of prendre in the main clause, but since it's the subjet of the subordinate clause, you must use the relative pronoun qui.

• Nous prenons le train. Un train (subject) part à 10 heures. → Nous prenons le train qui part à 10 heures.

• Nous prenons le train. Nous avons choisi un train (direct objet). → Nous prenons le train que nous avons choisi.

In French there are two main relative pronouns, qui and que. The choice between qui and que in French depends solely on the grammatical role, subject or direct object, that the relative pronoun plays in the subordinate clause.
Qui functions as the subject of the subordinate clause.
Que functions as the direct object of the subordinate clause
pror1: relative pronouns: qui and que

 

[Maître Capello]

Likewise, train may be the subject of the main clause and still use qui or que as relative pronoun depending on the relative clause. The choice of the relative pronoun is indeed independent of the part of speech of the antecedent in the main clause; it depends entirely on the part of speech of the relative pronoun itself in the relative clause.

Nous avons pris le train qui part à 10 heures. (le train = direct object in the main clause; qui = subject pronoun in the relative clause)
Nous avons pris le train que nous avons choisi. (le train = direct object in the main clause; que = direct object in the relative clause)
Le train qui part à 10 heures est arrivé en retard. (le train = subject in the main clause; qui = subject pronoun in the relative clause)
Le train que nous avons pris est arrivé en retard. (le train = subject in the main clause; que = direct object pronoun in the relative clause)

For more details, see also FR: que / qui - pronoms relatifs.