This document discusses various cost concepts that are relevant for business operations and decision making. It groups the concepts into accounting cost concepts and analytical cost concepts. Some key accounting cost concepts discussed include opportunity cost vs actual cost, business cost vs full cost, explicit vs implicit cost, and out-of-pocket vs book cost. Analytical cost concepts discussed include fixed vs variable cost, total/average/marginal cost, short-run vs long-run cost, incremental vs sunk cost, historical vs replacement cost, and private vs social cost.