Guild Wars 2

Does the Air IV trait and the Signet of Air stack? or what stacks and what doesn’t? I don’t see a speed stat, so I can’t tell.

The highest instance of movespeed increase is applied, it doesn’t stack.

So if you have Swiftness (33% MS bonus) and Signet of Air (25% MS bonus) then your character will be moving 33% faster because of Swiftness while Signet of Air will have no effect on you (until the Swiftness runs out.)

I think he means will the 5% move speed add on top of the 25% speed from signet of air.

As answered above, but with a different example, no.
25% speed will be applied, the 5% will not stack on top to give 30% speed. Silly I know, but what can you do.

thank you, I am still learning all of this.