Geometry at the top of the bodice
A straight neckline draws a level line across the front of the gown. Its width and height affect how it frames the chest and shoulders; the edge may be sharply horizontal or softened slightly at the center. Straps or sleeves can continue the line in different ways.
Compare the front with the side view to see where the edge meets the arm. The straight shape describes the neckline only. It does not tell you whether the dress is strapless or how the bodice is supported, so support and construction vary by dress. A straight upper edge is one option among vestidos de novia sin tirantes.
One edge, different silhouettes
Milos pairs a straight, strapless edge with lace and tulle. Alegra also has a straight strapless neckline: its close-fitting base becomes much fuller with a removable overskirt. The upper geometry can remain similar while fabric and skirt proportions change the whole image. The detachable overskirt alters the lower outline while the upper edge stays straight.