Men’s suit jackets generally contain an interlining to help keep the shape of the jackets and there are three different kinds, Fused, Half-Canvassed and Full Canvassed. Whereas women have more curves than men, so an unstructured jacket is more appropriate.
Canvassed jackets follow more of a traditional construction. Men’s suits were made with a layer of horsehair canvas under a wool fabric shell. This canvas helps hold the shape of the suit and kept it from sagging or deforming. Think of it as the foundation of house that helps keep it upright. Over time as you wear the jacket, the canvas conforms to your body shape and creates an amazing fit. The result is a clean, well put together suit that allows the fabric to drape naturally. However, hand sewing this interlining is a very labor-intensive process so it is much more expensive to make.
Fused jackets make up a vast majority of all suits that are sold off the rack. A fused interlining is glued to the wool shell of the jacket and is heat treated to remain there permanently. This process is much less labor intensive than hand sewing the canvas to the shell, so it is therefore cheaper. In the past over time the glue would wear out and the interlining would detach from the shell, causing what is known as bubbling. However, with technological improvements this is very rare.
There is a middle ground between these two structures; the half-canvassed jacket. Half-canvassed jackets have canvas material running only through the chest and lapels of the jacket. Past that point, the jacket is fused. The benefits of half-canvassed jackets are they generally have a lower price than a fully canvassed jacket and while still maintaining some of the advantages. Less handiwork means a lower overall cost.
An unstructured jacket is just as it sounds, there is no interlining structure. For men they are a lot more informal and lighter, but for women it is the proper construction because of their natural curves. Creating an unstructured jacket is actually more labor intensive than a fused canvas jacket as it requires a bit more work to protect the integrity of the jacket.