Curries-what is most essential?

Pataks Curry paste is my defining ingredient. Nutmeg wouldn't be something I would associate with curry. It comes from Indonesia, so wrong cuisine, I'd think.

If you’re talking Indian then it’s very regional but I would say most curries have some combination of some or all of garlic, ginger, cumin, coriander, turmeric and garam masala (which is itself a blend of different spices)

For me, it is a bit broader than a specific ingredient, but my essential for a decent curry is good quality and fresh spices.

There's no point in calling out one specific ingredient as curries are so varied in nature.

Thai basil essential for thai curries

I would think that Cumin would be a defining ingredient in a lot of curries. But as others have mentioned there are lots of variations and each could have their own specific defining ingredients.

I use Thai Gold coconut milk for my curries. 99% coconut extract 🤩

https://www.thaigold.eu/en/product/coconut-milk#ingredients

I don't thing there are any rules that we can say define a curry. But…

That sounds like spiced vegetable soup, not curry.

I'd consider that a premade sauce base, rather than a proper ingredient. The ingredients are what's used to make it. I use thai pastes a lot for the base.
FWIW, Massaman Curry contains nutmeg, and it originated in Indonesia.

It's added to thai curries (and spicy thai food generally), but it's pretty optional. But it's not really used to make the various curry pastes that determine what curry it is. I'd have kaffir lime leaf is more essential, but even then its not in every time.
Corriander seed?

As mentioned above base sauces and also the dry roasting of spices at the beginning . Marinade meats in yoghurt depending on the dish. Over all I think a large part is Ingedients and technique

The Indian curry club or whatever it's called thread from this site years ago is the closest to restaurant style curry I've ever made. Takes a bit of time but worth it if you freeze batches of the sauce base.

Chutney, if it aint got chutney it aint for me.

as second poster indicated, it is an umbrella term for many dishes that typically include the base ingredients of chilli & turmeric. After that it is any number of additional ingredients, pretty much always including garlic & onion, but can include combinations of the following:

Ginger, galangal, fenugreek, curry leaves, coconut, tomato, coriander, cumin, cardamom, kaffir like leaves, basil, fish sauce, lemon grass, poppy seed, soy sauce, peppercorn, spinach, yoghurt, Chinese 5 spice, sugar, and many more depending on the Asian regional cooking style.

Most typically the term curry is applied to Indian cooking styles

My understanding it's more of a restaurant approach that traditional. So they can prep and prepare multiple dishes to order in a reasonable time. Where a Indian "homestyle" is simply making dinner in a batch for everyone.

But I don't think the base/gravy is not authentic Indian. I've heard it described as hotel style, assuming this is how hotel or restaurant chefs in India would also work.

Though I would have said that Curry being synonymous with Indian is more of a British thing. I style expect "Chinese" style take away curry to be more common by a margin in Ireland. Which obviously isn't really Chinese. Apart from being heavily adapted, I think recall reading that the universal "irish chinese" menu was influenced heavily by Malaysian dishes as the first restaurants in the 50s beign set up by Malaysian Chinese immigrants.