What is margin in an equity transaction?

In an equity transaction,marginrefers to the loan that a dealer extends to a client to facilitate the purchase of securities. The client pays a portion of the purchase price (the margin requirement), while the dealer provides the remainder as a loan. This enables clients to leverage their investments and potentially enhance returns, albeit with increased risk.

Other options:

Amount paid by a client when using credit to buy securities: Describes the margin requirement but does not fully define margin.

Good-faith deposit to ensure future financial obligations: Refers to initial margin in derivatives trading, not equity transactions.

Interest paid by the client to borrow securities: Refers to short-selling, not buying on margin.

References:

Volume 1, Chapter 9:Equity Transactions, section on "Margin Accounts" explains the mechanics of margin trading and loans​.