The middle ground between relations in general and the sign relations informing logic, inquiry, and communication is occupied by triadic relations, also called ternary or 3‑place relations.

Triadic relations are some of the most pervasive in mathematics, over and above the importance of sign relations for logic.

For a primer on triadic relations, with examples from mathematics and semiotics, see the article linked below.

• Triadic Relations • OEIS Wiki • Wikiversity

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