What is the parlay: the short version

Weighing both sides of "What is the parlay?" leads to one event. Hedging and arbitrage both mean betting on more than one side of the same event. A hedge does it after a first bet is already placed, to lock in part of a win or cut a loss. Arbitrage does it at the start, across different books whose prices disagree, so that every outcome returns a little more than the total stake. What they share is the arithmetic of splitting stakes between results on opposite sides.

What does a hedge bet mean in practice? A bettor holds a ticket that now looks likely to win, or likely to lose, and places a second bet on the opposite result. How does hedge betting work in numbers? A parlay needing one last leg at long odds can be hedged by backing the other side of that leg, so the bettor collects something whichever way it goes, at the cost of part of the upside first hoped for.

How much to hedge a bet depends on the aim. To guarantee the same return on both sides, divide the first ticket's potential return by the decimal odds of the opposite side, and stake that. To only cover the first stake, bet less. Should I hedge my bet is a question about risk: every hedge pays the book's margin a second time, so a hedge bet strategy used on every ticket slowly costs real money.

Asked about this

Does hedging every bet cost money?

Yes. Each hedge pays the book's margin a second time, so a habit of hedging every ticket slowly eats into the overall return.

Is arbitrage betting worth the time it takes?

Gaps are usually one or two percent and last minutes, so the return has to be weighed against the hours spent searching for them.

How can a bettor tell that an arbitrage exists?

Add up one divided by each best price across all outcomes; when the total falls below one, the prices leave room for a guaranteed return.

What is a palpable error in arbitrage betting?

A price the book considers obviously wrong can be voided under its terms, leaving the other half of the arbitrage standing alone.