How we cite our quotes: (chapter.paragraph)
Quote #7
"I need you to become the place you became for Draco Malfoy…" (21.102)
Harry tries to activate the Room of Requirement by using his thoughts only. Throughout Harry Potter and the Half-Blood Prince, the young witches and wizards begin to learn how to conduct magic silently, using their mind alone. Here, we see Harry struggle with this complex kind of magic.
Quote #8
"It is Voldemort's fault that you were able to see into his thoughts, his ambitions, that you even understood the snakelike language in which he gives orders, and yet, Harry, despite your privileged insight into Voldemort's world (which, incidentally, is a gift any Death Eater would kill to have), you have never been seduced by the Dark Arts, never, even for a second, shown the slightest desire to become one of Voldemort's followers!" (23.152)
It is Voldemort who gives Harry access into his Dark mind and to his Dark thoughts. Harry and Voldemort share an intense connection precisely because Voldemort built that connection. Harry communicates with Voldemort in a way that no other person is able to.
Quote #9
As they flew over the dark, twisting lane down which they had walked earlier, Harry heard, over the whistling of the night air in his ears, Dumbledore muttering in some strange language again. He thought he understood why as he felt his broom shudder when they flew over the boundary wall into the grounds: Dumbledore was undoing the enchantments he himself had set around the castle so they could enter at speed. (27.45)
Language is used to not only communicate feelings, wants, and needs in Harry Potter, but it is also used to perform magic. It is a means of survival.