Many nouns in Tamil end in Ç£ -am; these can be items such as ¾À£ maram `tree', loans from Sanskrit like âÚÀ£ duuram `distance', and loans from English like öÕöÓ¹£ sistam `system'. In fact any English word that phonetically ends in the sequence [ '025 m] (`system, problem, museum,' etc.) will be treated as belonging to this group. Sanskrit nouns that end in [-a] are borrowed in their accusative form ([-am]) into Tamil.
All such Ç£ am ending nouns change this to Ç¢â att(u)
before adding case: ¾À£ maram 
¾À¢â
marattu. This form is known as the `oblique' stem of the noun.