Iteration in software development carries two complementary meanings: in programming, it refers to the repeated execution of a block of code, typically through loops such as for, while, or forEach, that processes elements in a collection or repeats an operation until a condition is met. In project management and agile methodologies, an iteration is a fixed time period (usually one to four weeks) during which a development team plans, builds, tests, and delivers a working increment of software.
From a programming perspective, iteration is one of the fundamental control flow mechanisms alongside sequencing and branching. Modern languages provide rich iteration abstractions including iterators, generators, and higher-order functions like map, filter, and reduce that express repetitive operations declaratively. Understanding iteration complexity matters for writing performant code, as nested iterations can quickly escalate time complexity from linear to quadratic or worse.
In the agile context, iterative development is the practice of building software incrementally through repeated cycles of feedback and refinement. Each iteration produces a potentially shippable product increment, allowing teams to gather user feedback early, adapt to changing requirements, and reduce the risk of delivering software that misses the mark. Frameworks like Scrum formalize iterations as "sprints," while Kanban takes a continuous flow approach that still embodies iterative improvement through regular retrospectives and process adjustments.