Put more directly: all choices are costs. Specifically, a choice is choosing to incur opportunity cost in order to realize some outcome. E.g. Buying a sandwich

Put more directly: all choices are costs. Specifically, a choice is choosing to incur opportunity cost in order to realize some outcome. E.g. Buying a sandwich so you can eat it to be full is choosing not to spend that $10 on anything else. In durable and intellectual domains, choices can incur opportunity costs, but also lead to switching costs in the future. I've always understood technical debt to be the combination of opportunity costs and switching costs resultant from a specific choice that resulted in a durable physical or intellectual good. In this way, technical debt is not a particularly complicated topic. The issue is that switching costs can be very high, and to eliminate the accumulated opportunity cost and switching costs of a previous decision, it is necessary to incur a new set of costs going forward. There is no "debt", there is only cost. The idea that you can "owe" on a series of choices implies that you can "pay it back". This is false. You can make choices - some may be more costly than others both immediately and in the future - but all choices have costs always. To quote Rush, "if you choose not to decide, you still have made a choice".