What is the difference in action between a Medium fast (med-fast) and moderate fast (mod-fast) rod/blank typically? Or is med-fast just a typo and they mean mod-fast? Have you seen any blank/rod catalogs with both descriptions?

Every med-fast and mod-fast blank I have gotten I did not like. But then again I like a fast blank.
To me they have no power. It is almost like.
They all seen to bend way into the middle of the blank.

Bill - willierods.com

Medium = Moderate. It is just verbiage. Heck, all of it is to an extent. There are "mod-fast" blanks that have a faster action than other blanks rated as "fast". Everything is subjective and the labeling has much to do with the manufacturer AND the class of blank family (spinning, spin/jig, popping, etc.).

“They all seem to bend way into the middle of the blank.”

That is because they are designed to do that.

Depending on the technique an angler is using there can be great benefits to using moderate blanks.

Medium and moderate mean the same thing.

Action is where a blank initially flexes. Fast action blanks initially flex in their upper 1/3rd. Medium or moderate initially in the upper 1/2, and slow initially along their full length.

The combination of terms such as Medium-Fast is a small attempt to expand on what is a very limited resolution of a very subjective system.

.............

Gary,
I think that everyone is right.
Check out the library -
Essentially you have the following actions in a rod.
Slow
Moderalte
Fast
Extra fast

Each of these words defines as to where the rod begans to bend. i.e. slow begans to bend from the butt, moderate or medium begans to bend in the middle, fast begans to bend at about the 1/3 way from the tip, extra fast begans to bend at about 1/4 from the tip.

Each of these rods are great when used for their particular purpose.
Just don't make the mistake in trying to use an extra fast rod, for an application that is better serviced by a slow action rod.
A good example of the extra fast rod is one that is used for vertical jigging. On the other hand, a down rigger rod is a perfect example of a slow action rod, as are many trout and steel head rods.

Take care
Roger

Roger, I think I might state that in another manner, ie. It is where the rod bending begins to stiffen, as all the bending begins at the tip, and a "fast action" stiffens up nearer the tip then a slower action.