What it is
A ground is a unit of land area used mainly in and around Chennai, equal to about 2,400 square feet, roughly 223 square metres — larger than a cent, which is the unit more commonly used elsewhere in Tamil Nadu. It's the customary way plots are described and priced in Chennai-region real estate conversations, even though the underlying legal extent on a patta-chitta or sale deed may be recorded in square feet or cents rather than grounds. The term is a market convention more than a formally defined revenue-department unit.
Why it matters when you buy
Since ground is a market term rather than the unit used on official records, always check the actual extent stated in square feet or cents on the sale deed, patta-chitta, and FMB sketch, and convert to grounds yourself if that's the unit you're thinking in. Relying on a verbally quoted number of grounds without checking the document's own figure is a common way buyers end up surprised by the actual size or price per unit area of a plot.
Where you find it
You won't typically find ground as a recorded unit on the patta-chitta or FMB sketch themselves; those record extent in square feet, cents, or hectares-and-ares. Ground mostly appears in listings, conversations, and sale negotiations for Chennai-area property. Before you rely on a quoted extent in grounds, convert it and compare against the precise figure on the plot's own documents.