Idly rice is not a marketing term. It is a specific short, parboiled rice ground with urad dal to make the batter for idli and dosa, and using the wrong rice is the most common reason a batter fails to rise.

The parboiling is what makes it ferment properly.

Soak it with urad dal and fenugreek, grind to a batter, and leave it somewhere warm overnight. The next morning you have idli, and the day after that the leftover batter makes better dosa than the fresh stuff.

Stocked with the rice at Curry Corner, North Melbourne.