Note: For around 6 years (2008 to 2014), this was the list of features presented by Temple of the Roguelike as a “Roguelike definition”. I have since replaced this view with my Traditional Roguelike interpretation.
by Slash, priest of the Temple of the Roguelike, 2008
| High-Value Factors | |
| Random Environment Generation | The game world and its contents are mostly procedurally generated with each game. |
| Permafailure (including Permadeath) | The character must pay for your mistakes and choices, sometimes at the cost of his life. Restoring games is discouraged and only provided to allow continuing split games. |
| Turn Based Interaction | All entities in the game world are queued in an endless loop and get their independent discrete turn to act. |
| Single command set | You can access all game commands from any place into the game. There are no artificial restrictions on what actions are available in a given game situation, for example inside or outside battles. |
| Freeform | Your advancement is not routed into a linear progression. You get to choose what to do, how and when. |
| Discovery mechanics | You must research or find out the nature and usages of the items into the world. |
| Middle-Value Factors | |
| Single player | You control a single character |
| Plenty of content | There are enough monsters types and items to make it worthwhile exploring. This is in contrast to a small set of known item and monster types. (more than 24 monster and item types is a good measure) |
| Complex non-trivial world and object interactions | Items have non-trivial usages, you can do some things which may not be obvious for the item nature. |
| Low-Value Factors | |
| High ramped difficulty | The game gets hard very quick and you are very unlikely to win until you have acquired enough experience. |
| Monsters are players | The nature of the monsters is similar to the player, they can have equipment, player-like stats, artificial intelligence and are subject to the same world rules |
| Character-based display | The player interacts with the world via a user interface based on character symbols that represent UI artifacts and entities in the world. |
| Hack and Slash | Gameplay involves around killing things to become more powerful and acquiring treasure to buy better equipment and repeat the cycle |
Temple of The Roguelike 
“It has since being replaced by the Classic Roguelike definition.” – this page should link to that.
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Could be this one, though it’s titled differently:
http://www.roguetemple.com/2014/08/25/a-new-roguelike-interpretation/
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