RAI

In Dungeons & Dragons (DnD) and other RPGs, RAI stands for "rules as intended." Players and Dungeon Masters (DMs) invoke the concept of RAI when describing how a game action should function, regardless of the actual, written rules that govern that action.

For example, when a player attempts to climb a rock wall in DnD, in-game rules describe how difficult the climb is and what actions a player must perform to successfully climb the wall. However, players playing as particularly athletic characters may argue that of course their characters can climb the wall, and using the RAI, they should not have to perform a skill check to determine whether their climb is successful.

Strict DMs, however, will likely use the RAW, or "rules as written," to force characters to roll a die that determines how skillfully they climb the wall. Who knows? The player might roll a 1, allowing the DM's real fun to begin.