THE THREE R's
Reduce, Reuse and Recycle in software engineer are about getting the most for your investments.
Reduce wasted effort in software development, focus on the design and utilize an iterative approach to continually engage with the users an keep the requirements current whilst regularly delivering functioanality.
Reuse what you have, 'if its not broken - don't fix it',. Leverage your existing investments and legacy systems. Blend the old with the new through abstraction and interface design. Break things into small reusable components to speed up delivery.
Recycle by continually improving, looking at what you have what works and challenging the thinking, making things generic at each iteration.