Quarantine - A restraint placed on an operation to protect the public against a health hazard. A ship may be quaran­tined so that it cannot leave a protected point. During the quarantine period, the Q flag is hoisted.

Quoin - A wedge–shaped piece of timber used to secure barrels against movement.

Quota - The quantity of goods that may be imported without restriction during a set period of time.

Quotation - An offer to sell goods at a stated price and under stated terms.

Quay - A structure attached to land to which a vessel is moored.See also Pier and Dock.