Before we talk about spices, we had probably better try to agree on a definition of what a spice is.
A spice is part of a plant, or a plant derivative, which when mixed with or cooked with other foodstuffs, modifies or enhances their flavour. Or both. And that very obviously includes herbs. Don't propose to get involved with the semantics of this, because your opinion is as valid as ours. Just to say that there is no 'heat' in, say, Galangal; but there is in Rocket and Mizuna........so we'll not try to differentiate between the two, otherwise we'll be cooking a meal with the spice coriander in it and then garnishing it with the herb coriander.
That may seem to be a 'catch-all' definition, but it does cover everything from the Carolina Reaper to Monosodium Glutamate, neither of which we would want to cook with. But folk do.
Don't know whether anyone is as interested in the subject as we are, but we'll just have a dig at defining flavour before we get to the individual spices, because it will inform some of what we say about them.
Flavour is a combination of the compounds that hit your nasal receptors as you breathe in prior to putting food into your mouth, and the overall hit of sweet, savoury(umami), sour, salt and bitter that you get as you exhale. It is remarkable how little disinterested research has gone into our sense of taste. Of course, the major food companies spend billions on research, but they keep what they discover very close to their chests.
Spices lose their nature over time, because the compounds which give them their properties are very volatile. Give 'em half a chance and away into the ether they go. This is not a conspiracy put about by spice merchants, just unfortunate fact. Lost count of the lovely people who don't need any spice because they bought lots from a Moroccan souk ten years ago. The best you can do is take the advice of the Wilburys and keep it in a cool, dark place. And hope.
So this is an alphabetical listing of everything we can think of which is covered by the above definition. Please let us know if we have missed out your favourite spice. BUT, just before we hit the tracks, let's make clear that although we will be listing every fact, rumour and bit of wishful thinking we know of for every spice, we want to make it abundantly clear that not one of them, nairy a one, is an aphrodisiac. Guess how we know. Maybe there's a glimmer with crushed green cardamom pods, but we think that may be more to do with the gin we float them in.....
AJOWAN SEEDS (Ajwain, Carom)
Choc full of Thymol, which gives it a distinctive aroma of Thyme, it is a native of Southern India. Used extensively in all types of flatbread and pulse dishes, Ajowan appears to have a genuine calming effect on the digestive system. Cooks in the Middle-East sometimes use the ground seeds.
ALLSPICE (see PIMENTO