Transferable skills
Skills that carry over between technologies. Transfers run fast within a discipline and slow across disciplines.
What it tells you about a developer
A history of successful transfers, visible as new stacks appearing and reaching real output quickly, signals learning speed. Many teams weight that above any single listed skill.
A backend developer moving between similar languages, or a frontend developer moving between frameworks in the same ecosystem, typically ramps in weeks. A move across disciplines, such as frontend to machine learning, takes months or years and is a genuine gap. This distinction is the practical basis for deciding when a missed requirement is still submittable.