Monotone vs Duotone?

I want to create 2 t-shirt designs - 1 using 1 color and the other 2.

For the 1 color, would I use a monotone or duotone?
I always thought the background color counted, so thats why the term DUOtone applied, but now I'm rethinking that.

I found this "duotone" tutorial using thresholds:
http://www.creativepro.com/article/turn-color-photos-duotones-photoshop

Original:


Here's the final product:

Is that actually a MONOtone?

Using the Duotone dialog box, I created these...

Monotone
Does this truly only use 1 color ink?
If the first pic, is also a monotone, is there some other terminology to distinguish between the 2?


Duotone using green & black.
Even though the true green rarely shows, it still only uses 2 inks because the green mixes with the black?

THANKS!

Just a reference as to what or how many inks are used in a multitone image
Monotone grayscale images printed with a single ink
Duotone grayscale images printed with two inks
Tritone grayscale images printed with three inks
Quadtone grayscale images printed with four ink