A swallowtail is a large, colorful butterfly with distinctive wing tips that extend backward in two points, like the forked tail of a swallow bird. These elegant butterflies are found on every continent except Antarctica, often visiting gardens where they float from flower to flower sipping nectar.

The eastern tiger swallowtail, common across much of the United States, displays bold yellow and black stripes on wings that can span five inches. Some swallowtails have tails so long and delicate they seem to trail behind as the butterfly glides through the air. Scientists believe these tail extensions might help the butterfly survive: when a bird attacks, it often grabs the tail rather than the butterfly's body, allowing the swallowtail to escape with just a torn wing tip.

The word also describes anything shaped like a swallowtail butterfly's wings. A swallowtail joint in woodworking looks like a row of interlocking butterfly wings, creating an incredibly strong connection between two pieces of wood. A swallowtail coat (also called a tailcoat) has two long fabric tails hanging down the back, worn at very formal events.