Mer-

{
  "id": "MLC-T-CHM-007191",
  "term": "Mer-",
  "field": "Chemistry",
  "definition": "A stereochemical descriptor used in coordination chemistry to denote a meridional isomer, where three identical ligands occupy positions around the central atom that lie on a meridian of an octahedron. This arrangement is distinct from the facial (fac-) isomer. It is commonly used for octahedral complexes with the general formula MA3B3.",
  "see_also": [
    "coordination",
    "cis, trans"
  ],
  "references": [
    "Red Book, 3rd ed., p. 245"
  ],
  "url": "https://mlchart.com/terminology/chemistry/mer/"
}