Term Kind Topic What it is
Cross-Functional Requirement concept Functional vs Non-Functional A quality the system must exhibit across its features rather than a behaviour it must perform, so named because it cuts across all functionality.
Functional vs Non-Functional Behaviour vs Quality of Behaviour concept Functional vs Non-Functional Functional requirements say what the system does; non-functional requirements say how well, and only the second constrains structure.
Non-Functional Budget Quality Attribute Budget, Latency Budget Allocation practice Functional vs Non-Functional Splitting a system-level quality target into per-component allowances with named owners, so a change can be shown to have spent someone's allowance rather than merely argued about.