The casualness of a midi dress comes down to two factors: fabric and silhouette. Cotton, jersey, linen, and knit fabrics all read as relaxed and easy. Tiered hems, wrap styles, and A-line cuts naturally reinforce that casual feel. Satin, bodycon cuts, or structured pleating shift a midi straight into formal territory. For everyday wear, prioritise breathable fabrics in unfussy patterns. Styling does the rest of the work: sneakers and flat sandals keep it casual and relaxed, while pointed heels and structured handbags dress it up.