> ## Documentation Index
> Fetch the complete documentation index at: https://docs.allium.so/llms.txt
> Use this file to discover all available pages before exploring further.

# Concepts

> Funding, open interest, mark and index price, positions, and liquidations on perpetual futures.

Shared glossary for perpetual futures. Venue pages name the tables and columns for each protocol.

## Perpetual Future

A derivative that tracks an underlying index price with no expiry. A funding mechanism keeps the traded (mark) price anchored to the index over time.

## Mark Price vs Index Price

* **Index price** — reference price of the underlying, typically an oracle or blended spot feed.
* **Mark price** — the price used for margining, PnL, and liquidation. Usually the index plus a bounded premium from the perp's own order book.

## Funding Rate

Periodic payment exchanged directly between longs and shorts to pull the mark price toward the index. A positive rate means longs pay shorts; negative means shorts pay longs.

Funding intervals differ by venue — hourly on some venues, every 8 hours on others.

## Open Interest

Total notional of outstanding perp positions in a market. Open interest counts each contract once, not both sides. Some venues split the figure by long and short.

## Positions

Per-account open exposure in a market — side, size, entry price, and (where the venue publishes it) unrealized PnL. Delivered as latest snapshots and daily end-of-day snapshots where those tables exist.

## Liquidations

Forced close of a position when margin falls below the maintenance requirement. Liquidation events carry market, side, size, and liquidation price where the venue publishes them.

## Units

Notional and contract units differ by venue. See that venue's table page for the unit on each column.