Not one cuisine but a continent's worth, unified by how spices are handled rather than by what is cooked.
What most menus label Indian is usually North Indian: wheat breads rather than rice as the staple, dairy used generously, and gravies built on onion and tomato cooked down in fat. It is the style that travelled furthest, because tandoor cooking and rich gravies survive a restaurant kitchen better than the more delicate regional traditions do.
Dishes to know: Butter Chicken, Chicken Biryani, Garlic Naan
The most common restaurant format abroad: a Nepali kitchen cooking a mostly Indian menu, with momo on the side.
Indo-Nepali is less a culinary tradition than a business reality. Nepali migrants opened kitchens in cities where customers already knew and wanted Indian food, so the menu is largely North Indian with the Nepali dishes the cooks actually grew up on sitting alongside it. The momo are usually the tell, and usually the best thing on the menu.
Dishes to know: Chicken Momo, Buff Momo, Chicken Curry
Lighter, sourer and less oily than its neighbours, built around a tray of rice, lentils and greens.
Nepali food is quieter than Indian food. Less cream, less oil, and heat that arrives as a sharp pickle on the side rather than being cooked through the dish. The everyday meal is dal bhat — rice, thin lentil soup, a vegetable and pickle — eaten twice a day by most of the country, and the restaurant menu is essentially that plus momo.
Dishes to know: Chicken Momo, Buff Momo, Dal Bhat
High-altitude food: noodles, dumplings and broth, built for cold and thin air rather than for spice.
Himalayan menus draw on Tibetan and high-hill Nepali cooking, where little grows and a meal has to be warming and calorie-dense. Expect wheat rather than rice, broth rather than gravy, and a spice level far below anything on an Indian menu. The food is closer to Central Asia than to the subcontinent.
Dishes to know: Chicken Momo, Buff Momo, Veg Momo
Rice, lentils and fermentation — a lighter, sourer tradition with almost no relation to a North Indian menu.
South Indian cooking is built on rice and lentils rather than wheat and dairy, and on fermentation rather than slow-browned onion. Dosa, idli and vada all start from a batter left to ferment overnight. Coconut, curry leaf, mustard seed and tamarind do the work that cream and garam masala do further north, and the result is lighter, sharper and often vegetarian by default.
Dishes to know: Veg Thali, Steamed Basmati Rice, Dal Tadka