A moth is usually a duller, night-flying insect with feathery antennae, while a butterfly is usually a brighter, day-flying insect with large patterned wings. As a rough memory hook, moths come out with the moon and gather at porch lights, while butterflies come out with the sun.
The core difference
Moth and butterfly both name flying insects in the same order, told apart mainly by colouring, antennae shape, and when they are active.
- moth — a flying insect related to the butterfly, usually active at night and less colorful, with feathery antennae: a moth kept circling the porch light.
- butterfly — an insect with large, often brightly patterned wings, known for its delicate flight: a monarch butterfly landed on the flower.
How to tell them apart
The antennae are one of the more reliable clues: a moth's antennae are typically feathery or saw-edged, while a butterfly's are thin with a small club at the tip. Time of day is a useful shortcut too, since most moths fly at night and most butterflies fly in daylight, though there are exceptions on both sides.
Butterfly has also drifted well beyond the insect. It is used as a verb for slicing meat open flat before cooking, and it names a swimming stroke where both arms circle together while the legs kick, so context usually makes clear which sense is meant.
