Number of days allowed in a charterparty that a ship may use a dock for loading/unloading before demurrage is payable to the shipowner. The lay days may be either (a) fixed as to number; or (b) indeterminate dependent on the circumstances, e.g. ‘according to the custom of the port.
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The period which is allowed for the loading and unloading of the ship. The counting of lay days begins after the arrival of the ship and serving the notice to the shipper.

The return of premium allowed under the returns clause by marine insurers when the vessel is out of use.

A horizontal stratum of cover within a structure of layers. For example, a primary insurer covers £100,000, the first excess insurer covers the next layer up to £200,000, the second excess insurers takes in excess of £200,000 up to £300,000 and so on. Layering spreads the risk among insurers or reinsurers and is applied to both property and liability insurances. See EXCESS INSURANCE.