Volume 1 - Linkages
Book 1 - Two Kinds of One-to-One Relationship
Chapter 1 - Affecting
The blank is a thing. A thing can be important or unimportant. A thing is usually important. The blank is unimportant.
Affecting relates one thing to one thing.
The verb to affect (he affects, they affect, he affected, it is affected, he is affecting) implies the affecting relation.
Definition: a thing is linked if it affects something or something affects it.
Definition: a thing is unlinked if it is not linked.