How to tell a sportcoat from an orphaned suit jacket

Hard to say, but with the ticket pocket and surgeon's cuffs I would think that it could certainly be worn as a sportcoat.

Follow your gut.

Suit jacket for sure.

If you can't tell the difference, why do you want to know?

Certainly looks like an orphan to me.

Maybe so but he is just asking for guidelines as to how to tell the difference. Surely someone has an idea?!

The problem is nothing stops a designer from breaking the "rules". Of course this assumes the OP cares about the rules.

Unless the jacket is some how marked all you can do is decide if you'd wear it.

Certainly no fixed rule, but often suit jackets have buttons that closely match the fabric, which makes sense since the trousers will use the same buttons and contrasting buttons would look out of place on them. SCs sometimes have more interesting buttons. If you are worried that the jacket looks too much like an orphan, swap out the buttons with something else (like horn) to add some contrast and visual interest.
Fred

Suit coat.

Closer to a blazer than a sports coat, which means it is far away from a sports coat.

You can usually tell by the fabric in this case it looks like worsted wool, to me this means is an orphan jacket. Look for fabrics that has more surface interest like hopsack, tweeds or anything that distinguish the fabric from worsted suit wool.

Feel and experience. There are no rules per se but it is usually very apparent. In any event if it is your own coat you will know its origin, if it is second hand then presumably it is an irrelevance given that you are happy to indulge in that market in the first instance.

A sportcoat is considered more casual than the orphaned suit.
 

Sorry for the thread revive, but I figured a thread revive would be better than starting a new thread and getting a bunch of "use the search button" responses.

I'm still confused as to what the real difference is between a suit jacket, sport coat, and a blazer.

Specifically, from what I gather, a solid navy sport coat with matching colored buttons made on the formal side is essentially the same as a suit coat.

I only ask because I got a sport coat/blazer, whatever the terminology is, made from a navy wool super 120 (IIRC) with matching navy buttons that was on the more formal side from Mr.Ned.
The fit is sublime and it looks great IMO when I wear it with a collared shirt, some dress jeans, dress shoes, for a night out on the town.
But, from what I gather, it's no different than an orphaned suit jacket except that it wasn't made as a pair with trousers...ever.

I gather that the "rules" would dictate that a sport coat or a blazer from using a more coarse thread and have a wider range of styling choices, but is there some overlap with a more formal solid sport coat and a solid colored suit jacket?