What it is
A cent is a small unit of land measurement widely used across Tamil Nadu and the rest of south India, equal to one-hundredth of an acre — about 435.6 square feet, or roughly 40.5 square metres. It's the everyday unit for pricing and describing house plots and small parcels, the way a ground is used in and around Chennai. You'll see extents quoted in cents on sale deeds and patta-chitta entries for smaller holdings, and in everyday conversation about land prices, even though larger rural extents are recorded in hectares and ares.
Why it matters when you buy
Because cents are the common unit for quoting plot prices, it's worth being comfortable converting between cents, square feet, and the hectares-and-ares figures that appear on official rural records, so you can sanity-check that the extent quoted to you matches what's on the patta-chitta and the FMB sketch. A plot advertised as a round number of cents can sometimes be a rounded or approximate figure rather than the precise surveyed extent, so treat the document's own extent as the one that governs.
Where you find it
The precise, legally recorded extent of a plot comes from the FMB sketch and the patta-chitta, both of which may state area in different units depending on whether the land is urban or rural, or convert between cents, square feet, and hectares-and-ares. When an extent matters for a transaction, use the figure from these official records rather than a rounded figure used in conversation or advertising.