According to AWS 3.0 2001 (Yeah, yeah! I know it's an old out of date version but, it's all I had!):
"Root Pass" - A weld pass made to produce a root bead (page 32).... Well, that doesn't tell us much so, let's dig further...
"root" - A nonstandard term when used for "joint root" or "weld root (page 32). Hmmm...
"root bead" okay let's look that up...
"root bead" - A weld bead that extends into or includes part or all of the joint root (page 32)... I'm still not satisfied are you?
So, let's look at
"joint root" - That portion of a joint to be welded where the members approach closest to each other. In cross section, the joint root may be either a point, a line, or an area. See figure 4 (page 22)... And
"joint" is defined as: The junction of members or the edges of members that are to be joined or have been joined (page 22)...
Now we're getting somewhere... So let's go see how a
"weld root" is defined...
"weld root" - The points, shown in cross section, at which the weld metal intersects the base metal and extends furthest into the weld joint (page 44). See figures 24(B)-(E), 24(H)-(K), 24(M)-(P)... Confused? You shouldn't be by now so, that's how I go about understanding what the AWS defines
"root pass."So, if you want to use your own words to better describe what a
"root pass" really means, then go for it!
Besides, I'm tired and am up way past my bed time friend so, I apologize for leaving the rest to you... I hope this helped somewhat.
Respectfully,
Henry