A friend is many things - someone you like, someone you know, someone you trust.

And that was why she thought they'd never become friends.

They had met in all the wrong ways. He had picked on her friend, her best friend, and the one who had taught her about the magical world.

She couldn't like him, not even when he moved over to make room for her by the Gryffindor table after her Sorting.

And she disliked him even more the next morning, watching him pull tricks and small pranks at everyone, especially the Slytherins. She sat across him when he gave his older cousin, Narcissa, a mustache, and she was right behind him when he tripped the small Hufflepuff boy rushing past him.

They had argued after that. She had never been able to stand bullying, and he was the worst bully she had ever seen.

A friend was someone you liked.

She didn't like him at all.

They would have spent the next five years almost hating each other, if they hadn't decided to be indifferent to the other's existence. He, for James's sake and she, for Remus's.

Because James was his best friend, his best friend who was head over heels for her. And because she actually liked Remus, who spent time in the library with her and gave her chocolate when she was homesick, that first week at Hogwarts.

So they, quietly, silently, and on their own, decided to avoid and ignore each other to the best of their abilities.

But even she knew something was wrong when he ran down the dormitory stairs, with a letter in his hand, and flew out of the Fat Lady's portrait.

With tears running down both cheeks.

Everyone had noticed and for once, the Gryffindor common room was silent.

It was silent for a full five seconds, until there was a thundering down the stairs, and James skidded to a stop in front of her.

"Where'd he go?" James looked around him wildly, his fingers moving crazily and nervously, and an almost terrified look in his eyes.

She had wordlessly pointed at the common room door, staring at the unusually dishevelled Marauder. James nodded his thanks and tore out the door.

That was the first time James had spoken to her without the slightest hint of hitting on her.

The common room had broken into whispers as Remus and Peter soberly walked down the stairs. Quietly, Remus took up a seat beside her, and at her questioning, hesitantly told her that Sirius had received a letter from his father that contained "bad news."

No amount of questions would persuade Remus to tell her what the "bad news" was, but with a little Slytherin manoeuvring of her own, she learned about how Sirius's father could be cold and cruel, how his mother yelled and screamed and cursed, and how his beloved baby brother was too scared to even talk to Sirius, for fear of being alienated from the rest of his family.

A friend was someone you knew.

She didn't know him at all.

For a little while, there was something about him that scared her. There was something in his eyes, a little downcast at one moment, and then full of angry fire the next. He seemed unpredictable and his temper always ran high.

Later, James would confide to her that that period had been Sirius's dark times. There were times that he had felt that the Marauders were his only friends in the world, the ones who kept him sane.

And James was best at doing that because James was not just his best friend anymore – James was his brother now, too.

So she could understand the slight resentment Sirius had for her when she and James had started dating in seventh year. She was stealing James away from them - from him – on Hogsmeade trips, some nights in the common room, all the things he and James used to do together.

So she always encouraged James to spend as much time with his mates that last year at Hogwarts. She told herself she did that because she had compassion for Sirius and knew what it was like to feel as if you were losing a friend.

But there was a small part of her that knew that she did that because that small part was just a bit afraid of Sirius Black.

A friend was someone you trusted.

She didn't trust him.

She didn't know how wrong she was until they had all gathered for another Order of the Phoenix meeting.

That was back when she and James weren't married yet, although they were going strong – stronger than ever. She knew she loved James and that James loved her, and that their love was the kind that lasted a lifetime.

So when Dumbledore asked if James and Sirius would go take one of the most dangerous missions she had ever heard of, and James had accepted with a grim nod, it was all she could do not to argue. Argue with Dumbledore, argue with James, argue with Moody even, whose only role in the whole thing was that he had given Dumbledore the information that led to the mission.

But she hadn't argued because she and James had talked about it before and had agreed that the cause was more important now, more eminent and more vital than either of them or their relationship.

So instead, she waited until James was preoccupied with Dumbledore and Moody, making plans for their departure. Then she had excused herself, walked upstairs to a hidden corner and cried.

Plain and simply cried.

And she had never been more surprised, when the door had suddenly opened and she had been swept into a familiar someone's arms, with her head against his chest.

She had looked up in mid-hiccup and her surprised eyes met Sirius's determined ones, as he slipped a chocolate bar in her hand. Then she lay her head back down on his shoulder again as he said, quietly and roughly, "Don't worry, Evans. I'll take care of him. I promise – I'll bring James back home safe to you."

And in that moment, she realized how much she liked Sirius (with all his chocolate and hugs), how well she knew Sirius (after years of spending time with him and James), and how she trusted Sirius (as she believed in his promise with all her heart).

So when they had come home from their extremely dangerous mission, Sirius had a broken arm, some burns, and a limp while James came away with hardly a scratch.

Lily had greeted James with one long kiss, before slipping away to Sirius's side and giving him a sisterly kiss on the cheek. Then she slipped a necklace around his neck, one with all the manly dragon claws on it and one very special pendant in the middle – the one with the picture of a lily and a dog, with the word "Friends" beneath it.

Because a friend is many things - someone you like, someone you know, someone you trust.

Sirius Black was her friend.