See: Base Premium, Premium Base, Subject Premium.
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A ceding company’s premium to which the reinsurance premium rate (factor) is applied to produce the reinsurance premium. In other words, the reinsurance premium is a percentage of the ceding company’s premium.

See: Basis of Attachment.
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Simplistically, the segregation of all premiums and losses attributable to policies having an inception or renewal date within a given 12 month period.
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Underwriting result based on written premiums and ultimate losses from loss events falling within the same accounting period, where the accounting period is the period covered by the insurance policy or reinsurance agreement, regardless of when the premiums and losses are actually reported, booked, or paid. See Accident year experience and Calendar year experience. Underwriting losses are typically offset by investment income.