The lead time is the time between when a product is ordered, and when it is received and available.

Its interpretation differs slightly depending on the agent or organisation involved. Procurement lead time is the time between when the order is placed and when the goods are received in the country. For a health facility, the lead time is the time between when the request for stock is placed with the central medical store in the country, and when the goods are received at the facility.

A program design, management, and evaluation tool that describes the main elements of a program and how these elements work together to reach a particular goal. The basic elements in describing the implementation of a program and its effects are: inputs, activities or processes, outputs, outcomes, and impacts. A logic model graphically presents the logical progression and relationship of these elements.

A dynamic planning and management tool that logically relates the main elements in program and project design and helps ensure that an intervention is likely to achieve measurable results. It helps to identify strategic elements (inputs, outputs, purposes, goal) of a program, their causal relationships, and the external factors that may influence success or failure. It can provide the basis for monitoring progress achieved and evaluating program results.