The incremental build model is a software development lifecycle model in which the system is built and delivered in a series of increments, each adding functional capability to the previous one. The first increment delivers a working core; subsequent increments add features until the full system is complete.

Increment 1: [core functionality]           → delivered, working
Increment 2: [core] + [feature A]           → delivered, working
Increment 3: [core] + [feature A] + [B]     → delivered, working
...

Each increment goes through its own mini-cycle of design, development, and testing. The result after each increment is a working, testable product rather than a partial system that only functions when all pieces are in place.

In the waterfall model, the full system is designed, built, and tested before any of it is delivered. The customer sees nothing until the end. If requirements were misunderstood or priorities changed, there is no practical opportunity to correct course.

The incremental model addresses this by producing something deliverable and usable early. Feedback from real use of increment 1 can reshape priorities for increment 2. This is the same motivation as Agile iterative development, though the incremental model predates agile as a formal concept.

Incremental and iterative are often used interchangeably but are technically distinct. Incremental means adding new functionality with each cycle. Iterative means revisiting and refining existing functionality. Real Agile processes like Scrum are both: each sprint adds new features (incremental) and refines existing ones based on feedback (iterative).

The incremental model is a natural fit for embedded and systems software where a minimal working hardware+firmware baseline must be established first before peripheral features can be added on top.