The A-line silhouette is named for its triangular shape, fitting at the bodice and widening continuously toward the hem.
An A-line garment creates a visual outline resembling the capital letter A. In wedding dresses, the shape usually follows the torso before gradually flaring from the waist or high hip to the floor. This gives the wearer more movement than a tightly fitted skirt while remaining less voluminous than a traditional ball gown.
The term became especially influential in fashion after Christian Dior introduced his A-line collection in 1955. Although flared garments existed earlier, the label helped establish the silhouette as a recognizable design category.
A-line is often confused with a ball gown because both can have full skirts. The difference is construction and volume: a ball gown generally has a fitted bodice and a dramatically full skirt, while an A-line widens more smoothly and continuously. It is also distinct from a mermaid shape, which stays close to the body before flaring near the lower leg.