Definition
A-line describes a silhouette that is fitted at the top, at the waist or shoulders, and widens gradually toward the hem, like a capital letter A.
The name was popularized by Christian Dior, whose spring 1955 collection was called the A-line. Today it describes any garment that flares gently and evenly from a fitted top: skirts, dresses, coats and tops.
An A-line skirt fits at the waist and over the hips, then flares to the hem. It takes its shape from waist darts or a contoured yoke and from side seams angled outward, and it has much less fullness than a circle skirt. That makes it economical with fabric, flattering on many figures and easy to sew: a classic first fitted skirt.
An A-line dress flares from the shoulders or bust without a waist seam, or from a fitted bodice, as on a fit-and-flare dress with an A-line skirt.
Fabric choice changes the effect. Medium-weight wovens with some body, such as cotton twill, linen, denim, corduroy and wool, keep the A shape crisp; softer fabrics make it drape closer to the body.
To add flare at the hem without width at the waist, the pattern piece is slashed and spread from the hem, or godets are inserted. Sewly's A-line skirt is drafted from your waist and hip measurements, with a waistband and zip or a pull-on elastic waist.