All blazers are jackets but not all jackets are blazers.... it's beginning to sound like Algebra.
According to Wikipedia
A jacket is a type of sleeved hip- or waist-length garment for the upper torso. A jacket is generally shorter, ending just below the waist, and often lighter. Some jackets are fashionable, while others serve as protective clothing.
Blazer, similar to but more casual than a suit jacket; single- or double-breasted of sturdy material, commonly with metal buttons.
I've even read definitions that include striped cloth school or club colors.
So the search for the Blazer....
When I think of a Blazer, I think of school blazers...like Thom Browne's collection for Brooks Brother's under the Black Fleece label.
The net-a-porter.com versions.....
Now to peruse my patterns for possible blazer candidates...
I'm thinking 7421 is my best bet, I'll just have to tweak the collar a little, and drop the neckline.
I had to look at what's available at the Vogue website and didn't find a lot, but I did find
McCalls 6172 - Palmer Pletsch jacket in three lengths, and that one on the right looks like a silhouette Stella McCartney has been showing in her spring collections.
Butterick 4610 - Looks like a nice pattern for a basic blazer you could do a lot with.