In RE, tools support ↑requirements management as well as modeling, documenting, and validating ↑requirements.
1. In general: The ability to establish explicit relationships between related ↑work products or ↑items within work products.
2. In RE: The ability to trace a ↑requirement
(a) back to its origins,
(b) forward to its implementation in design and code and its associated tests,
(c) to requirements it depends on (and vice-versa).