When a restaurant opens a new branch, the head chef writes a standardized recipe card. Not "slow-cooked chicken." The card reads: chicken thigh 180 g · oil temp 78°C ± 2 · cook time 90 min · salt ratio 1.2%.
The menu description lets guests imagine the dish. The recipe card lets any kitchen reproduce it exactly. Same dish, two different languages for two different readers.
Context Grammar works the same way. The narrative in a portfolio chapter lets a designer understand a scene. The Spec lets an iPhone, a fridge, and a car dashboard act on that scene correctly — without anyone re-explaining it three times.