"Sir"

The year had been uneventful so far. Severus taught a bunch of idiots and tried not to flinch when someone called them 'Sir', and Harry continued his schooling having done well in his OWLs.

Severus was teaching a sixth year nonverbal spells class containing one Harry Potter, trust him to be the one to disturb the peace. They had just performed a, frankly, rather harsh, demonstration on the boy, and he had, understandably, shouted the first spell that came to his mind, accidentally pushing the professor backwards with the power of it.

Honestly, Severus was rather impressed with the force of the spell but they couldn't be seen going soft so, once they had straightened their robes, they quickly told Harry, "Do you remember me telling you we were practising nonverbal spells, Potter?"

"Yes," Harry replied, looking surprised by what he had done.

"Yes, sir," Severus said firmly though the words left a foul taste in their mouth.

Harry appeared confused for a split second, but then a knowing gleam entered his eyes and he said, without missing a beat, "There's no need to call me 'sir', Professor."

The words shocked them, they knew they should give the boy detention for his sass, but they also didn't want to know how they would have felt if they had heard the boy speak that horrid word to them for the first time in six years, so they simply said, "Class dismissed," and left the classroom.

– –

Harry Potter was… a curious person, that is how most people would describe the boy. Though he was near a spitting image of his father, his actions usually paralleled those of his mother. He was friends with few though was capable of being friendly with anyone. Some would say he was too nice to those who would see him dead. He didn’t see any of this, however; if asked, he would reply that he was just Harry as he always had been and always would be.

The list of those who agreed with this sentiment was short. Very short. In fact, it held only one name: Severus Snape. They didn’t think the boy anything remarkable. To them he was just a troublemaker, though they could admit that the trouble usually came to him, and not the other way around.

Despite this, somewhat questionably, shared opinion, the boy and the professor did not get along well. If either was asked they would forcefully argue that the other hated them, though this wasn’t actually true. Not deep, deep down, anyhow. They each, in their own way, cared for the other, perhaps more than was to be expected. The reason? They both knew, or in Harry’s case suspected, a secret no one else in the castle was aware of.

It was just a regular Thursday for Harry Potter, resident celebrity of Hogwarts school of Witchcraft and Wizardry. He had Defence first thing and though Ron was still complaining about their teacher being Professor Snape, Harry was looking forward to his favourite lesson even if the professor hated his guts.

As soon as they entered the classroom Snape announced that they would be working on nonverbal spells, something Harry had never attempted and so was nervous about trying. Naturally, Snape chose him for the demonstration and, in his panic, Harry ended up shouting the spell out loud. He had cast so strongly that Snape was flung all the way across the room and though he felt he should apologise, he knew from past experience that that was bound to amplify the situation.

With that thought in mind, he stood quietly while Snape got up and dusted themself off. They swiftly walked towards the boy, while Harry stood nervously, and only once they were in front of him did they ask, with a sneer, “Do you remember me telling you we were practising nonverbal spells, Potter?"

Harry decided he better not argue so simply replied, “Yes.”

He was not surprised when Snape appeared unsatisfied; they often were. He was, however, surprised when the next words out of their mouth were, “Yes, sir.”

He was confused. The professor flinched whenever some used the pronoun “he” for them, they had very nearly taken points, at the sound of the word “sir” before, so why were they telling him to use it? He didn’t understand why the professor was asking, no, commanding him to hurt them. Figuring he would rather risk detention than make them make that awful face, he gathered all the confidence he could and said, “There’s no need to call me ‘sir’, Professor.”

They looked shocked, for that matter, so did everyone in the classroom, but he couldn’t bring himself to regret his choice. Not when the professor dismissed them without taking so much as one point. Or when Ron looked at him with disbelief once they were a safe distance from Snape’s room. Not even when Snape gave him detention at the start of the next Defence lesson.