It is no coincidence that the words “hot” and “spicy” are phonetically different, and this is because they also happen to have different meanings. Especially in India for obvious reasons is a recurrent conversation and people normally ask me if I’m used to Indian food because it is spicy as Mexican.
I had my doubts about the interchangeability of these two words, so let´s see: A spice is a vegetative substance used in nutritionally insignificant quantities as a food additive mainly for flavor or color, while hot refers to the sensation of “burning”.
The point of confusion comes from weather these two words can be used interchangeably, and that certainly would not be completely correct. This is because there is a word coming from Old French called “Piquant”, or “Picante” in Spanish, which exists to avoid the ambiguity between spicy and hot (which evidently needs to be more promoted to justify its existence).
Some of the best examples I could find to illustrate this differences are a pumpkin pie, that can be spicy (due to ingredients such as cinnamon, nutmeg, allspice, mace and cloves) but is not actually piquant. Indian food for example is spicy and usually piquant as well, but this of course is relative to whoever is eating it (for me it is most of the times). Another example is a seasoned Italian sausage that may have all kinds of seasonings and flavor (spicy), but would not necessarily be hot.
On the other hand, Mexican food relies more on herbs, chili, and yes, some spices, but not in the abundant proportions of Indian food. So I guess the easiest way out of this words game is saying that I have no problem with hot or piquant food, but spices I just can´t handle.