The definition of the conditions under which a reinsurer or insurer becomes liable for a loss or multiple related losses under an excess of loss treaty or underlying policy. Most definitions provide for the aggregation of individual losses arising from the same event or originating cause to be treated as a single claim so that the (re)insured bears only one deductible. Where weatherrelated losses persist over a period the hours clause defines the loss occurrence. Latent disease liability claims may produce multiple claims over a period due to continued exposure of workers to the same harmful working conditions. Insurers may seek (perhaps with difficulty) to define the continuing working conditions as the single event or originating cause. See CLAIMS SERIES CLAUSE.