Lexicon · Measure
Capacity
It separates what appears affordable from what the structure can hold without weakening the future.
Canonical definition
Capacity is what a person can truly sustain after fixed obligations, pressure, and trajectory are accounted for.
Why capacity matters
A purchase, loan, move, subscription, or commitment can look affordable in isolation while still bending the trajectory.
Capacity asks whether the structure can absorb the choice across time, not only whether there is money today.