… or what makes a flat bar flat?

I’ve got a lovely Spank Oozy low riser bar on my bike; it has a small 5mm rise (its geometry is described as 4° Up and 6° back).

I’ve been having a look at some carbon flat bars and have been getting a tad confused about all the values. Superstar’s Helix flat bar is described as having 0° rise and 5° upsweep; can a bar have upsweep but no rise and just to confuse things further, Niner’s Flat Top bar (the name suggests it’s flat) has a 5mm rise. Thomson’s flat bar supposedly has an 8mm drop if reversed.

Am I confusing upsweep with rise and what differentiates a flat bar from a very low riser?

Rise is how far above the centreline of the bars at the stem the component mounting/narrow bit starts. Upsweep is the angle the component mounting/narrow bit deflects from horizontal. Back sweep is the same but from perpendicular to the bike frame axis.

Got that, thanks.