vocabularies

The set of units attested as the DENOMINATOR of a price rate — the 'per' of a per-measure price. A cross-dimension OVERLAY, not a new dimension: its members are the SAME unit terms that live in the measurement/counting vocabularies (u_each in QuantityUnits, u_gram/u_kilogram/u_ounce/u_pound in MassUnits, u_metre in LengthUnits, u_litre/u_millilitre in VolumeUnits, u_square_metre in AreaUnits), each carrying a SECOND member_of edge here (the dual-membership pattern, b123). Nothing is redeclared: 'priced per kg' and 'weighs 2 kg' share the identical u_kilogram term, so a read correlates them within-dimension (the units law, TANGIBLE-AXIS §2). The overlay exists because a numeral_unit property binds exactly one has_values_from vocabulary (read.ts validates against has_values_from[0]) and none of the per-dimension vocabularies spans the cross-dimension denominator set a rate needs. Membership is a POSITIVE, region-neutral attestation ('this unit has been seen as a price basis on a real shelf'), NEVER a claim that other units are invalid bases anywhere — a unit joins on a real attested instance (L12/L13), exactly as a growing vocabulary does; a base not yet listed (square-foot, square-yard, yard, and other regional measures) is deferred pending its first real instance, not forbidden.

Answers the question: price basis.