Game mechanics

A game mechanic is a term that is generally used to talk about a specific aspect of a game, though it is often used in a fluid manner. Here I try to boil down game mechanics into their more abstract forms.

Game Mechanics:

Mechanic	Description	Example
Binary Search
Combos
Diminishing Returns	This is a economic property which states that the increase of a single variable may benefit productivity at first, but as it continues to increase, the gain in productivity diminishes.
Equipment
Graph Traversal
Growth	There are many types of growth: linear, exponential, cubic, logarithmic, etc. Each changes the outcome dramatically. As time goes on, a particular variable increases and must be dealt with by the player.
Hidden Information	In this mechanic, there is information that they player is initially unaware of, and must try to figure it out using other mechanics.
Guessing	As the name implies, this mechanic involves trying to make the best guess for the correct answer. If the answer is entirely predictable, guessing not necessary, if it's entirely random, guessing isn't much fun.	In Rock, Paper Scissors you have to guess what your opponent is going to throw, which is random, but it's also based on past experiences and their own psychology.
Judging Opponents	Having to judge or predict what your opponents will do in a game.	Many games require you to have to interact with opponents in various ways, either by making alliances, deals, etc.
Markers
Memory	The requiring of a person to keep various pieces of information in their head at the same time, for a prolonged period of time.	The classic game, Memory, uses this, but so do many action games where you're expected to memorize a boss's movement patterns.
Movement Rate	For games that have moveable objects, this mechanic dictates the rate at which they can move. Games can be dramatically altered by changing this rate throughout the game, or by making it fixed.
Neighbor Count
Open Draw Pile
Optimal Path	An optimal path is the path between many possible nodes which best meets the specified criteria.	A common example if the Travelling Salesman Problem where the goal is to find the shortest path that allows you to stop at each of the necessary cities once and returns you home.
Optimal Set	An optimal set is the collection of objects from many possible objects that best fit a specified criteria.	A common example is the Knapsack Problem. Imagine you are in a treasure room with a knapsack with limited space. You want to take the most valuable treasures, but they all have to fit in the sack, so you must find the optimal combination.
Pattern Recognition	The ability to recognize patterns in seemingly patterned information.	In many games, obstacles follow a set pattern that can be discerned through study, and then exploited. Think boss battles.
Pickups
Race Tracks
Randomization	This is the introduction of a completely unpredictable element. A great many games rely on this to add variation, but too much of it is annoying. Be aware of pre-random vs. post-random.	Any game with dice, coin flipping, card shuffling, etc.
Reflexes	The rapid reaction to stimulus.	This is a major part of nearly every action game ever made.
Repeated Move Chains
Set Packing
Threes Optimization
Time Limit	Requiring the player to finish a task in a specified amount of time. This mechanic can be added to nearly every type of game, and usually makes a large difference to it. It can also be varied by not letting the player know how much time is remaining.
Token State Changes
Triadic Relationships