Reference
Reference is a phenomenon both of experience and thinking. It happens when a focal point for meaning is selected by the meaning-maker from the infinities of the world. The meaning—taking form as a mental representation, an act or object of communication, or an interpretation—“stands for” something in the world. Reference involves the specification of particular instances and general concepts, their circumstances as entities or actions, and their properties as qualities or quantities. Things in the world might be identified as entities or actions, though, by transposition actions may be construed as entities, and entities as actions. Entities and actions can be particular—a single instance—or multiple, defined in their generality as concepts. By transposition, by way of conceptualization, instances can be connected to the general. This connection of the instance to the general is by means of generalizable properties, including qualities and quantities.
Specification
Specification is the identification of something, either in its singularity (an instance), or its generality in more than one instance (a concept); also absences or meaningful non-specification.
Circumstance
Circumstance is defined in this grammar as whether something is conceived in terms of its condition as an entity or the actions constituting that entity.
Property
Property refers to those descriptive features of an entity or action, either in its singularity in the case of an instance at a moment in time, or in plurality when criterial features are captured within a concept in order to define the shared features of more than one entity or action. Properties may be variable in the case of an entity which is the subject of action, or capture the range of variability across instances within the scope of a concept. Properties may refer to qualities or quantities.
Reference: Cope, Bill and Mary Kalantzis, 2020, Making Sense: Reference, Agency and Structure in a Grammar of Multimodal Meaning, Cambridge UK: Cambridge University Press, pp. 77-78.