Bounded context
A bounded context is the boundary within which a particular domain model, its terms, rules, and invariants, is consistent and authoritative. The same business concept (e.g., 'Order') may exist in multiple bounded contexts (Sales Order, Fulfillment Order, Billing Order) with different attributes and lifecycles. The boundary is explicit; translation between contexts happens at the boundary.
Bounded contexts are the strategic-DDD answer to the question 'why does our 200-engineer codebase feel like a tangle?', usually because too many concepts cross boundaries without explicit translation. The diagnostic move is a context map: name every bounded context, draw the relationships (shared kernel, customer-supplier, anti-corruption layer, conformist), and identify where ambiguity lives. Bounded contexts often map well to team boundaries (Conway's Law) and to service boundaries in a microservices architecture; they don't have to, but the alignment is healthy when it happens.