Polymarket, a prediction market platform on the Ethereum blockchain, operates on a binary outcome model where each market has only two possible outcomes: YES or NO. This ensures that the total probability of all outcomes always equals 1, maintaining market efficiency. For instance, if an event occurs, the YES outcome is valued at $1 and NO at $0, and vice versa if the event does not occur. The platform's shared order book system mirrors this binary structure, allowing for efficient price discovery and liquidity concentration. Orders are matched based on the principle that YES + NO = 1, preventing arbitrage opportunities where the sum of probabilities is less than 1. This system ensures that any perceived arbitrage is instantly corrected by the market's internal mechanisms, maintaining balance and preventing exploitation. Polymarket's structure also supports multi-option markets, where each option is treated as an independent trade with its own YES and NO outcomes. This design allows for complex prediction scenarios while adhering to the fundamental rule of YES + NO = 1, ensuring consistent market integrity across various event types.