qualifier number + unit a measured amount

reference temperature

also called measured at

The temperature a viscosity figure was measured at, as a temperature. A viscosity without its temperature is not a weak statement but an empty one — the same oil reads 171 mm2/s at 40 C and 18.3 at 100 C — so it is required on every viscosity statement, exactly as b153's `filtration_rating` may not stand without its efficiency. It is a NUMERAL and deliberately not a token over a fixed set of reference points: the sheets read at the mint publish at least nine — 40 C and 100 C for kinematic viscosity everywhere, -40 C for a brake fluid's cold stiffness (TotalEnergies HBF 4, 880 mm2/s max) and for a Brookfield reading (TotalEnergies Fluidmatic MV LV, 11 200 cP), and -15 C, -20 C, -26 C and -30 C for the cold-cranking figures that Castrol prints across its range (GTX 20W-50 at -15 C, GTX Diesel 15W-40 at -20 C, Magnatec 5W-30 at -30 C, Castrol Axle EPX at -26 C), with SAE J306 defining three more at -12, -26 and -40 C. A closed token vocabulary would have thrown most of them away. It is the live b153 precedent of a numeral qualifying a numeral (`filtration_rating qualified_by filtration_efficiency`).

Reference temperature is a measured figure, given in °C.

It is a qualifier of dynamic viscosity — it has meaning only inside a dynamic viscosity statement, never on its own. It belongs with dynamic viscosity to measurement — its measurable, physical facts.

It is answered inside every dynamic viscosity statement, not as a standalone question on a kind.

answered with: №number + unit — a number paired with a unit drawn from an exhaustive unit vocabulary.
value domain: Temperature units — the vocabulary its answers are drawn from.
qualifier of: dynamic viscosity — required_one per statement — it has meaning only inside that host's statement.

Answered inside every dynamic viscosity statement — not a standalone slot on any kind.