---
title: Markets and Trading
description: Understand binary markets, YES-side pricing, order matching, positions, and the order instructions available through UDX.
---

A market asks a question with a YES or NO result. Trading always uses the YES contract.

## Market Structure

| Term | Meaning |
| --- | --- |
| **Series** | A group of related markets. |
| **Event** | The real-world question that resolves YES or NO. |
| **Market** | The tradable contract and its order book. |
| **Contract** | The quantity being bought or sold. |

A winning contract settles to $1.00. A losing contract settles to $0.00.

## Trade the YES Contract

- `BUY` YES opens or adds to a long position.
- `SELL` YES opens or adds to a short position.

There is no separate NO contract. Buying NO at $0.40 is economically equivalent to selling YES at $0.60.

A position is the signed net quantity of YES contracts. Positive is long YES; negative is short YES.

## Prices and Quantities

Prices are in dollars and must follow the market's tick size. Quantities can be as small as `0.01` contracts.

Use decimal strings from the API for price and quantity calculations. Do not convert them to binary floating-point values.

## Orders and Trades

An order remains open until it matches, expires, or is canceled. A match creates a trade and updates the account's position.

See [Place an Order](/api-reference/orders/createorder) for supported order fields and time-in-force values.