So, if i have just Precise, i can re-roll one dice. right

45 minutes ago, zhentil said:

So, if i have just Precise, i can re-roll one dice. right

Aim allows you to reroll 2 dice. Precise X increases it by X. So Precise 1 allows 3 rerolls, Precise 2 allows 4. And all dice need to be rerolled at the same time.

1 hour ago, zhentil said:

So, if i have just Precise, i can re-roll one dice. right

Precise can only be used when spending an aim token.

From what I can tell unit keyword is something that is a blanket ability assigned to a unit not to models or other objects, while weapon keywords are abilities applied to each weapon that is used. For unit keywords I see it as as long as you have the keyword from different sources (STrooper precise 1 and scopes for instance) that they stack in that way.