It wasn't that Spock was against swearing for moral reasons – though he always raised an eyebrow when Bones went on one of his curse-filled tangents, the one that clearly stated humans are so peculiar and I find this amusing – but Jim had always figured that cursing was one of those illogical concepts that Vulcans tolerated from humans, but never partook in themselves.

So, needless to say, he nearly fell off his chair when Spock murmured, "Damn" after Jim had checked him yet again at chess. Jim tried to look as if falling halfway out of his chair had been an orchestrated move, but well, even he wasn't that smooth.

Spock raised an eyebrow at Jim, this one broadcasting, I don't know what you are doing, but I find it amusing, which was different in that it was usually directed solely at Jim, instead of at humanity as a whole. Jim caught himself staring and wondered if perhaps he needed to stop naming Spock's eyebrow expressions, if only for the sake of his own sanity.

"Captain?" his first officer intoned. "Are you feeling well?"

"I'm fine, Spock," Jim said, trying to look at his first officer's eyes instead of his eyebrows. It was strangely difficult for some reason. "Just, you never…you know," he gestured broadly, and probably very stupidly. Jim blamed the eyebrows. "Swear," he finished lamely.

"Vulcans have no use for curse words, as their use often denotes anger or frustration, both of which Vulcans do not feel," Spock said. "However, while they are not prevalent among Vulcans, they are among humans. I have read that this is due to a number of health and social benefits that cursing brings, and am curious to see if these benefits can apply to myself." Spock lifted his shoulders in a facsimile of a shrug. "I am doubtful that they will, but I believe my findings will still be useful, as this is also designed as a cultural experiment in order to better understand the human majority aboard this ship."

"How logical," Jim said. "But, you know, you could've just said that you're doing it for the hell of it."

"Vulcans do not do things 'for the hell of it,'" Spock said, not quite frowning, but not exactly not frowning either – too often, Jim found that Spock's expressions could only be defined by their negative space, by what they weren't. "As science officer, one of my duties is-"

"I was joking, Spock," Jim said, smiling. "Another human cultural behavior."

"How fascinating. Perhaps I should attempt an experiment in humor as well, after my current investigation is concluded," Spock said dryly.

Jim smirked, turning his eyes to the chess board that had been forgotten in the last few minutes. "You know, if you're going to swear, you could at least use something better than 'damn'. Like 'fuck.'" Jim looked up to see his first officer staring at him strangely, a light green tint appearing on the Vulcan's cheeks. Jim almost rolled his eyes. How did the Vulcan expect to conduct this experiment if he couldn't even hear a swear word without blushing? "Your move," he said, nodding towards the chess board, and after a careful nod, Spock became enraptured in the game once again.

It turned out that Jim giving Spock pointers on how to swear was a huge mistake. Jim had almost forgotten about the Vulcan's experiment by the end of the day, because he honestly did have other things to think about other than Spock, even if it didn't always seem like it.

The experiment was brought to the forefront of Jim's mind in the canteen the following morning. Spock was making comments upon their last diplomatic mission, when he quietly interrupted himself to sigh, "Oh shit," sounding as if he were merely commenting on the weather. The replicator in front of him was smoking and producing things that didn't look at all edible – though with Vulcan food it was sometimes difficult to tell.

Spock, of course, was dealing with it with his usual intelligence and aplomb, while Jim stood frozen in place, his mouth gaping open. Why had he advised his first officer to take his swearing to the next level again? His face felt flushed, which he reasoned was only a result of surprise. However that didn't quite explain why he suddenly found it incredibly difficult to not look at his first officer's ass as the Vulcan bent over to tinker with the replicator, and fuck, when had any word, let alone that particular one, ever sounded so smooth and delicate?

Jim obviously needed to get a grip if a single word – a perfectly normal word! – was unhinging him like this. Then again, it was probably just the smoke from the replicator going to his head. Spock glanced at Jim, the Vulcan staring for a moment before giving him a raised eyebrow that hopefully didn't mean, you are aroused and I find this amusing. "Could you help me with this replicator, Jim?" he said slowly. "It is being," he paused, "a pain in the ass." Jim ducked his head up and down in an approximation of a nod before helping his first officer with the malfunctioning machine. And if Jim found it a little hard to catch his breath after they were done, well, Jim blamed the smoke for that too.

"Fuck," Spock murmured.

Jim wouldn't have said that the entire bridge fell silent at the first officer's proclamation – that would be a bit overdramatic – but suddenly the room seemed to be filled with the sound of everyone not peeking over their shoulders at Spock. It was deafening, but at least everyone was too busy not looking at Spock to even bother noticing Jim. Because Jim's pants suddenly felt a bit tight and he had to cover his mouth with his hand to prevent himself from smiling too hard. Or from moaning. To be honest, Jim wasn't sure what would happen if he let his mouth do what it wanted right now.

Determinedly not thinking about his mouth and the things it wanted to do, Jim stared at Spock, who continued to work at his station, a faint crease in his forehead the only betrayal of any frustration. Well, that and the profanity. Jim maybe needed to get a grip, because if Spock could unspool him like this by just saying a swear word, Jim wasn't going to last until the end of this experiment.

When he tore his gaze away from Spock, he found Uhura staring at him and raising an eyebrow that definitely meant, I know you are aroused and I find it amusing. Maybe he should stop letting her hang around Spock so often. Jim only raised an eyebrow in return until she rolled her eyes and turned back to her station. When Jim turned back to Spock, he found the Vulcan staring at the two of them curiously, his lips twitching.

Jim did not blush as he got back to work, and damn any communication officers who said otherwise.

His ears seemed to somehow have become attuned to the frequency of Spock's voice. Without even meaning to Jim hung on every word that Spock said, just waiting for those few muttered curses like a man in a desert might wait for a drop of rain. The worst part was that Spock had clearly chosen a favorite swear word, softly sighing, "fuck" during any encountered frustrations. Most of which seemed to happen around Jim. Coincidentally, Jim had also been taking a lot of cold showers recently.

At the end of the week, Jim found himself once again playing chess with Spock, trying not to look at his first officer's eyebrows or eyes, or really in his general vicinity. But for some reason his brain didn't seem to get the phrase "out of sight, out of mind," and Jim kept finding his thoughts circulating around the Vulcan before him, none of them the least bit interested in the chess match.

"Oh fuck," Spock observed, and Jim fought the blush crowding his cheeks – since when had he become so delicate? – as he looked at his first officer, who was eyeing the chess board with what seemed to be amusement.

"Huh?" Jim said intelligently.

"You seem to have me in check," Spock explained, "and I was merely expressing frustration with a curse word. Is that a problem?"

Jim ignored what Spock said and squinted at the chess board. "Are you letting me win?" Suddenly Spock's words caught up with him. "Frustration?" You said Vulcans don't feel frustration."

Spock's lips only twitched. He eyed Jim as if he were a small child: adorable, but ultimately incomprehensible and someone to whom things must be patiently and repeatedly explained. "What would I gain by letting you win?" he asked. "And why would I swear if not to express frustration?"

Jim narrowed his eyes as the Vulcan looked at him. Say what you want, but Jim Kirk was tactical genius, even if it took a bit longer for realizations to come when they concerned his enigmatic first officer. He recognized strategy when he saw it. "You're doing this on purpose, aren't you?"

Spock only raised an eyebrow. "What the fuck are you talking about, Captain?" he said with his usual poise and politeness, and it really shouldn't be possible to sound so innocent while saying something like that. But even as Jim's gaze was drawn to the graze of teeth against lips as Spock swore, he also saw the hint of a smile in his first officer's eyes.

"You are doing this on purpose!" he groaned, putting his face in his hands. "Oh my God, Spock, was this whole thing jut to mess with me?"

"On the contrary, I was truthful when I first explained my experiment to you. However, given new data," Spock said, his eyes moving slowly over Jim in a way that didn't seem to be entirely scientific, "I decided to shift that focus of the study."


Spock looked at him as if it were obvious. "To you, Jim."

Jim's insides twisted and he tried not to let a grin take over his face, because he was still miffed at Spock. For some reason. He was having trouble remembering why, to be honest. "So you…you just…" he sputtered, while Spock's lips twitched again. Jim glared and said, "Do you get off on making me flustered or something?"

"Yes," Spock said.

"…Oh," Jim said. "Like…?"

"Yes," Spock said again, an eyebrow raising in what Jim could now officially identify as, You do not understand my seduction techniques, but I still enjoy watching you try. Which, fuck it, was enough of a challenge that it spurred Jim into action.

Jim leaned over the chess board and pressed their lips together, his breath catching as Spock's eyes slipped shut. The kiss, at first only a chaste press of lips, soon deepened into a clashing of mouths, and Jim found himself clutching at Spock's shoulder in order to keep his balance as the Vulcan sucked on his lower lip.

"Fuck," Jim panted against Spock's mouth, absently noting that his hand had somehow moved into Spock's hair, thoroughly mussing it. Good. Spock's own hands cradled Jim's cheeks, the Vulcan's eyes dark and his lips flushed green. "Fuck," Jim repeated.

"Yes," Spock breathed, "that would be acceptable." Before Jim could decide whether to laugh or to kiss Spock again, Spock made the decision for him, his hand guiding Jim's mouth back to his own as he maneuvered them towards the bed. "In fact," Spock said, barely breaking the kiss to speak, more so breathing the words against Jim's lips, "I believe we should proceed to fuck immediately."

Jim's eyes almost rolled into the back of his head as the curse sent a fresh flow of blood directly to his groin. "I can't believe you've been saying that word just to watch me be aroused," he said, letting his hands stroke Spock's sides as he kissed him again. One of his hands wandered down against Spock's own. He twined their fingers together, remembering what he'd heard about Vulcan kissing.

Spock's breath caught and he pushed Jim away before tackling him onto the bed. "Your arousal gave me unexpected pleasure," he said as he lifted Jim's shirt above his head. Jim proceeded to grind his hips against Spock, smirking. "How's that for arousal?" he asked, and Spock responded by growling and undoing Jim's pants with an alacrity that bordered on being frantic. Jim shoved Spock out of his own trousers and for a moment it was if they were meeting for the first time all over again, two dominant personalities wrestling for control, clashes of lips and teeth as they fought to get each other's clothes off, sucking livid bruises onto each other's skin as they lined up against each other, naked and moving senselessly, only seeking sweet friction that burned at Jim's gut.

Jim had never been more aroused in his entire life. He'd also ended up underneath Spock, but he was finding that he was okay with that. Jim stroked the back of Spock's thighs as Spock's hands roamed over his own body. Everywhere Spock touched sparked into sudden awareness, no part of him going unattended by Spock's sucks and bites and kisses. Jim returned the favor, sucking hard enough on the Vulcan's neck to make him gasp, letting his hands flit everywhere, cupping Spock's ass, caressing his arms, pumping at his dick. At one point Spock leaned down to lick slowly and deliberately up Jim's dick, his eyes never moving from Jim's. Jim gasped at the wet heat, his head dazed and empty at the sight of Spock staring at him as he licked and sucked. Jim's hips bucked and he had to pull Spock back up to him for fear of ending this too soon. Their lips met again and they kissed with a fervor that left Jim breathless.

Jim broke them apart in order to allow them both gasp in air, creating a natural pause in which Jim was content to simply look at Spock, to note how his dark eyes roved over Jim's legs and dick and chest, finally settling on his face. "Jim," Spock breathed, "I am satisfied that this is occurring. However, the sexual frustration I felt while waiting for you to realize you were attracted to me is now limiting my patience. I would appreciate it if you could fuck me now." Jim knew better now than to think that the curse was innocent, as Spock deliberately drew the word out, ending it with a sharp click on the k sound.

"Fuck, Spock," Jim gasped as Spock pulled Jim on top, grinding their hips together. He reached blindly for the lube on the bedside table – he may have been using it yesterday in order to get rid of some sexual frustration of his own – and coated his fingers with a shaking hand. As he pressed his finger against Spock's hole, he noted that it took very little prep to actually press in.

Spock gasped and pressed against his finger, answering the question Jim hadn't yet asked: "As I said, I have wanted this for a week. I took the liberty of fantasizing about you."

Jim groaned, his mind going blank at the thought of Spock naked and writhing in his room as he got off thinking about Jim. It sent him kissing trails across Spock's stomach as he twisted his finger inside of Spock, smiling as the Vulcan let out a choked breath.

"Still satisfactory?" Jim asked, smirking.

"Y-yes," Spock breathed, stuttering as Jim lifted one of the Vulcan's fingers to put in his mouth, rubbing his tongue against the pads of his fingers. Jim inserted another finger inside Spock, pumping them steadily as he sucked against Spock's fingers.

It was rare to see Spock's focus so singlehandedly consumed by something, as there were few things that ever merited all of that Vulcan brain power. Right now, however, Spock's eyes were fixed on Jim as if looking away might kill him. Spock seemed to be trying to keep as still as possible, but he couldn't help the little gasps he let out as Jim blew his fingers, or how his hips bucked every time Jim's fingertips teased over Spock's prostate. As Jim inserted a third finger in, Spock's hands flailed to grab Jim's face, the Vulcan leaning up so that their foreheads rested against each other. "Jim," Spock murmured, his eyelids drooped and his voice low and trembling, his usual control shot to hell. "Fuck. Me."

Jim could feel the lust and pure want cascading over him from where Spock's fingertips rested against his face. He gasped as he realized that it was Spock feeling all of those things, feeling them for Jim. Jim lifted one of Spock's hands between his own, and kissed the palm gently. Then, slicking himself with lube, he pushed inside Spock, both of their mouths opening in small, identical o's as Jim slid all the way in.

"Fuck," Spock groaned, and Jim laughed and playfully said, "Yes." He gave an experimental thrust that had Spock growling. "Faster," the Vulcan said, before taking the initiative and moving against Jim's dick in a way that made Jim's blood sing. He felt as if he were on a completely other plane of existence as he timed his thrusts to Spock's, the high of their fucking shrouding his mind and body in white-hot pleasure, pressure building up in his gut as he felt Spock tight and hot around him.

Spock's breath hitched every time Jim hit his prostate, the Vulcan groaning when Jim closed a hand around his dick. Spock's eyes still remained focused on Jim with a burning intensity as they moved together, their gasps in sync as Jim felt his lust and affection bleeding into the Vulcan and felt Spock's desire flowing into Jim in return. It was an intoxicating double pleasure that only heightened as Jim thrust faster and harder, too close to climax to do more than pound blindly into Spock, finally coming as he felt Spock's lips press against his, Spock's eyes wide open and staring into his own. Spock came only a second afterward, his eyes closing at last as pleasure overcame the both of them.

Jim collapsed on top of Spock, panting hard and unable to move. Spock's arms wrapped around him and Jim automatically nuzzled closer. "That," he said, "was…"

"Fascinating," Spock sighed, and Jim couldn't help but laugh at the sound of Spock sounding completely and utterly blissed out. At a raised eyebrow from Spock, Jim only laughed harder.

"I'm sorry," he wheezed, "it's just, you sound so happy."

Ordinarily Spock likely would have taken that as an insult, but now he could only seem to smile. Jim pulled out of Spock in order to lie more comfortably against him, deciding he liked this version of Spock whose hair in complete disarray and whose whole body flushed a light green.

Jim closed his eyes, absently kissing Spock's chest as the two of them caught their breath. Spock held Jim's hand in front of his face, spreading the fingers out and examining them. "I am happy," Spock admitted quietly.

Jim felt his heart burst a little, grinning against Spock's chest. "I guess that means you were right."

"Hmm?" Spock hummed, placing Jim's hand back at his side. He now seemed more preoccupied with brushing his fingers through Jim's hair than trying to deduce Jim's meaning. If only everyone else could see this side of Spock, so content and pliant. Then again, Jim didn't really feel like sharing this version of the Vulcan with anyone.

Jim attempted to raise his eyebrow at Spock, knowing from Spock's small smile that it was a bit of a futile effort. "Swearing does have health and social benefits," he smirked.

Spock leaned down to kiss Jim, a kiss that was more lazy and content than passionate. "It would appear so, though I can hardly say they were the ones I anticipated," Spock said. After a pause that Jim would almost cause hesitance, he said, "Though further data will need to be taken in order to verify our hypothesis."

Jim nodded gravely. "I agree. What kind of experiment has only one trial?"

"I am glad you see the validity of the scientific process," Spock said, his serious tone far outweighed by the way his fingers couldn't seem to stop touching Jim and how his eyes were once again fixed on his in wonder.

Jim grinned. "Ready for another go then?"

Spock thought for a moment and then smiled. "Fuck yes," he said with a glint in his eyes, and Jim groaned. God, did he love science.