Each skill is listed internally as a shorthand abbreviation. Below are graphs that depict each skill tree to their fullest extent. They are sorted in alphabetical order from left to right, with numeric characters taking priority.
Each abbreviation starts with the letter "S." This simply means "skill."
There are three common suffix that a skill can have. These are "A" for advanced, "E" for expert, or "M" for master. i.e. SCAHBEM for (Skill) Crafting Armor Heavy Boots (Expert) Master.
As you may have noticed, despite being the master skill, which is the final tier, it still contains the expert tag. This is required to maintain proper progression of skill trees. However, not every skill has an "advanced" suffix, instead being replaced by another descriptor such as "Boots," as shown in the above example. Regardless, all trees eventually have an "expert" (*) and "master" tag.
(*) Except the Fight tree in general. They split at the advanced and the expert tier and may have descriptive abbreviations instead of the common suffixes. i.e. SFM2SSM (Skill) Fight Melee 2(Handed) Slashing Sword Master
*: Can apply to any armor.
(*) Daggers utilize 1H crafted instead of Close Combat, unlike their fight tree.
(**) "Advanced Magic Amplifier Crafting" in game.
(*) Both pistol and rifle trees also include bowpistol and bowrifle, respectively.
SFM1B: 1H Smashing
SFM1P: 1H Piercing
SFM1S: 1H Slashing
SFM2B: 2H Smashing
SFM2P: 2H Piercing
SFM2S: 2H Slashing
SFMCA: Advanced Close Combat
(*) Also includes Bowpistol and Bowrifle, respectively.
Trees do not split further.
Trees do not split further.