A denomination is a unit of measurement: weight, money, amounts, numbers etc. For example; dollars are in denominations of 10s, 20s ,100s ; Weights are in denominations of Kilos/grams or pounds/ounces. Pre-the OS survey, various parts of Ireland used different denominations to describe area. Units of measure apparently included ploughland, carvagh, tate, and ceathru, with regional variations. The Irish and English acre were also not the same size. Part of the reason for Griffiths valuation and the OS survey was to standardise measurements across the country, to mitigate the resulting discrepancies in taxation. In Galway, I believe the measure was usually: Townland = 4 (or more) x ceathru (quarters) each containing 4x cartur (cartrons), each containing 4x cnagaire (croggery) Cathy