A runt is the smallest and weakest animal in a litter, the group of babies born at the same time to one mother. In a litter of puppies or piglets, the runt might be noticeably tinier than its brothers and sisters, struggling to get enough milk because the bigger siblings push it aside. Farmers and breeders often worry about runts because they start life at a disadvantage.

Runts sometimes don't survive without extra care and feeding. But with attention and good nutrition, many runts grow up just fine, even if they stay smaller than average. Some runts become perfectly healthy adults, just a bit more compact than their littermates.

People sometimes use runt as an insult, calling someone the “runt of the litter” to mean they're the smallest or weakest of a group. This usage can be mean-spirited, suggesting someone doesn't measure up to others. In stories, though, runts often become unlikely heroes. Wilbur, the pig in Charlotte's Web, starts as a runt that Fern saves, yet becomes the story's brave and beloved hero. The word reminds us that being small at the start doesn't determine how strong, capable, or remarkable someone can become.