Love
Love, a word as odd as humans themselves. It had a stupid amount of meanings and meant nothing but confusion. How in gogs name could the Humans think that such a silly thing could ever hold any sort of meaning to anyone when it was used so causal to refer to anything from a Moirail to an object?
Yes, the word Love was a stupid phrase and didn't mean anything at all to Karkat. He refused to accept that such an annoying, vague concept could ever actually hold any sort of meaning for anyone.
No matter how many times he told himself this, it was never quite true. Because every time that John would whisper that he loved him while he was snuggled into his side, he would swear that the temperature of his digestive track would rise.
Every single time that Dave would tell John and him that he loved them both while they were all about to fall asleep in bed, he would get the feeling that several flutterbeasts had become trapped in his stomach.
It had never made any sense to Karkat that such a meaningless, silly, useless word could bring on any of these effect, but somehow it did each time without fail.
Maybe, if he thought very hard about the matter, he might just come to the conclusion that the word itself may not hold any value to him, but the people saying it did. And both John and Dave would swear that in those few moments before they all fell asleep, they could just barely hear the words whispered back to them.