Wójtowicz/Normand's third FP category: any computation that is dependent on when it runs or how many times it runs. Examples: ship_items (exactly-once semantics), publishing events, reading a current user's geography, and Fermilab's HotBits geiger-tube random-number web service (true randomness from beta decay means every call produces an unpredictable result). Composition rule: anything that touches an action becomes an action (contaminated-swimming-pool analogy). The FP discipline is to push actions to the edges of the system so the rest can be understood as calculations and data. Purity-vs-side-effects is the wrong lens — what matters is whether behavior depends on when/how-many-times.