It's quite interesting that "boiling water" in many Slavic languages is actually a separate word (and not derived from "water", but from "boiling"; similar how the author mentions "ice" being used instead of "frozen water").
in the slavic languages do they have a different way to describe boiling or freezing milk, or any other liquid?
While these are not separate states of matter, they ARE special thermodynamic systems, with the particular property that they tend to remain exactly at the phase transition temperature while heat is added or removed from the system.
This is a somewhere esoteric technical distinction, but it has practical everyday consequences. It's why boiling food works so consistently as a universal cooking option.
You don't need to control the temperature of boiling water, it is an exact temperature that depends only on ambient pressure. As a consequence recipes work by only specifying time, sometimes with a single adjustment for people at higher altitudes.
This is remarkable given the wide variety of containers and heat sources used, and it is used practically by virtually every cooking tradition, even if it's reason for working is not common knowledge.
It shouldn't be surprising it'd acquire a single word as a unified concept.
edit: In those other languages is it like how we use ice? where water is the default, but it could mean any frozen liquid?
I would agree that "boiling milk" and "boiling oil" are very unlikely to get separate words, unless one of them happens to be an extremely common thing that people encounter a lot and that has special practical implications.
Milk might be a special case, in that it essentially is just water with some other stuff dissolved. It is to water as salt water is to water... but more so.
My guess would be that the single word might get pressed into service like "ice" does, but I think we'd have to find languages that include this word and survey native speakers. It could vary.
Nearly everyone encounters boiling water in everyday life, but do most people ever see other liquids boiling, even once, and especially during the historical periods that shaped our current languages? If not we might be getting into something like technical language, where daily life lines up poorly and terms and jargon get formalized.
Asking for the "reasons" behind a certain word existing is sort of like asking why the human body looks the way it does. Sure, scientists may have good theories why it was evolutionary advantageous to have five fingers and no tail, but in the end the only answer that's for certain is, "because it evolved that way". So the answer is, "we" have a word for boiling water because people found it useful to have such a word.
So English arguably has three unique words for the three common states of H2O.
When those technical distinctions are important we use specific technical terms for them (of which there are a few different ones for the phase transition - depending on discipline).
The cooking term is "rolling boil" which is a nice two word combo with a specific meaning.
I don't know how it is in other languages but in English "boiled water" and "boiling water" refer to different things - boiled water may be steam or water that has underwent some boiling, e.g. for sanitation, on the other hand "boiling water" refers strictly to water that is in the process of boiling.
I can see why some languages may have a separate word for one of these concepts to avoid some of the ambiguity.
I'm not a fan of extending the language with new words unless they are compound (with or without spaces) but extending the dictionaries with more and better descriptions is a no-brainer, there's a lot missing from them.
It depends on the tea, but some cannot be well made with a metal pot of water that's taken a few minutes to get from the kettle to the table.
The general rule of thumb is that black tea (i.e. fermented tea leaves) should be brewed at 100°C, green tea (non-fermented tea leaves) should be brewed around 80°C to avoid it being bitter and white tea (young, non-fermented tea leaves) is best at around 70°C.
Boiled water does have the extra connotation that it is presumed to be mostly sterile, which, while not hard to derive from the fact it has been boiling, is not immediately clear. After all the past tense does not tell us how recently it was boiled.
For that reason I'd argue that if one of boiling water and boiled water should be in the dictionary, it should be boiled water. Of the two, it is the term that potentially carries extra information.
If you're asking for isvann at a restaurant, you'd expect to get water with ice, not just very cold water.
But if you're talking about having gone bathing in isvann one spring, it specifically means in water that - whether or not there is actually ice in it - is cold enough that it might have recently melted.
(I'm a native speaker, but had to look up the precise nuance there to be sure I wasn't just making stuff up)