Stud

Studs are small, cylindrical bumps that are on top of most LEGO bricks that hold together the brick above it. All studs of LEGO Bricks have the word "LEGO" printed on them. Not all LEGO bricks have studs, there are some which have smooth sides and are studless (yet this pieces bear the word LEGO)."Stud" is also some times used as a unit of measurement. Example: 2x4 means two studs wide and four studs long.

Studs are the basis of all LEGO systems, and is used extensively in storylines by the Minifigures, a stud for them can be:
 * Currency
 * Unit of measurement
 * Basis of written Minifigure Language
 * Used on the Message Boards to show where a user ranks

In Video Games
In LEGO Star Wars: The Video Game, LEGO Star Wars II: The Original Trilogy, LEGO Star Wars: The Complete Saga, LEGO Indiana Jones: The Original Adventures, LEGO Indiana Jones 2: The Adventure Continues, BIONICLE Heroes, LEGO Batman: The Videogame, and LEGO Harry Potter: Years 1-4, studs serve as "token" items, as they are constantly found in every level of the game. They are used to buy new things in the shop of each game (in Dexter's Diner in LEGO Star Wars: The Video Game, Mos Eisley Cantina in LEGO Star Wars II: The Original Trilogy and LEGO Star Wars: The Complete Saga, Barnett College in LEGO Indiana Jones: The Original Adventures, Balta's store in BIONICLE Heroes, the Batcave and Arkham Asylum in LEGO Batman: The Video Game, and Diagon Alley in LEGO Harry Potter: Years 1-4) The studs are actually bricks known as "pips": round 1x1 plates. Silver studs are worth 10, golden studs are worth 100, blue studs are worth 1,000, and purple studs are worth 10,000.