Hi I'm a total beginner here. I found the most confusing part of this software is that there are way too may abbreviations. They slow me down a lot. For example, what's U or adata stands for?

Is there a full list(if it's possible)of all abbreviations in Houdini? Free or pay source are both welcomed. Thanks.

I havent seen such a list yet. How about you list these abbrevations and where you found them and the forum answers?

U is a the first part of UV, which is analogous to XY in the standard Cartesian plane i.e.
https://www.varsitytutors.com/hotmath/hotmath_help/topics/cartesian-plane [www.varsitytutors.com]

adata appears to be from an old Houdini version, and probably means attribute data, but you can display descriptive names in Vops rather than the shorterend one, in the preferences/Network Editor/Display VOP Input and Output Descriptive Labels

There wont be a full list anywhere as there is some presumed knowledge

start listing the abbreviations you're interested in in your original post like this:

ABC =
DEF =
etc

then people can reply, and you can update your original post to reflect the answers