phrasing space

The number of distinct ways you can say the same thing without changing its meaning — the more ways, the more room the expression has to survive mutation and clear the merger line.

A sentence like "the cat sat on the mat" has a small phrasing space (few ways to say it faithfully); a definition like "openness to experience is the tendency to seek and value novel stimuli for their own sake" has a large one (many faithful paraphrases). The size of the space is a property of the expression in relation to its field: a field with rich vocabulary and flexible syntax gives every definition more phrasings; a field with thin vocabulary and rigid syntax compresses every definition toward a single form.

The concept matters because copyright's merger doctrine says you cannot own what has only one way to be said — and the phrasing space is how many ways it can be said. A rich phrasing space means the expression is protectable (many forms, so the one you chose is expression not idea); a thin phrasing space means the expression merges with the idea and cannot be owned. The canary wing of the castle lives here: the craft of the moderate definition is finding the point where the phrasing space is large enough to clear the merger line but the definition is distinctive enough to detect if copied — the same detection-entitlement split the wing traces from every angle.

The phrasing space is field-specific (rich vocabulary widens it, thin vocabulary narrows it), form-specific (semantic binding leaves it intact, grammatical binding shrinks it), and convention-specific (academic prose's preference for conjunction and lexical cohesion over subordination preserves it, while fields that demand tight syntactic binding compress it toward the merger line).