Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.

[EX Q]: This is a question for English wordsmiths. Is there a word that 'feels' like the word 'ethereal' that means something ethereal that quickly disappears. Or is 'ethereal' the correct word choice for this? Ethereal was the first word that popped into my head for this. From the various definitions that I've looked at for ethereal, it says delicate, beautiful, heavenly, etc. but not necessarily quickly vanishing, except for the secondary definitions related to ether that suggests it evaporates. I'm just wondering if there is a better word than this. I'm using the term 'ethereal skill' to describe a certain type of pilot skill (instrument flying) that requires tremendous practice to achieve proficiency, and once proficiency is achieved it is a beautiful thing, but if you don't practice it regularly, that skill vanishes after a few weeks. USAGE: Instrument proficiency is an ethereal skill that once obtained must be maintained through constant and regular practice.
[EX A]: You are probably looking for the word ephemeral. ephemeral: Lasting for a very short time.

[EX Q]: There is a particular taste that I could never quite translate in English. It is not bitter, although it sometimes occurs with it. The best example is eating a raw quince fruit. The mouth and tongue get a sort of dry feeling. Similar taste can be experienced with some persimmon fruit, and unripe plums. I know the word in French (apre) and Bulgarian (). Google translates these as rough, but that somehow seems unlikely. Any ideas?.
[EX A]: Astringent, maybe? Astringent taste is the least common of all the 6 Tastes and can be found in legumes (such as beans and lentils), fruits (including cranberries, pomegranates, pears, and dried fruit), vegetables (such as, broccoli, cauliflower, artichoke, asparagus and turnip), grains (such as rye, buckwheat, and quinoa), spices and herbs (including turmeric and marjoram), coffee, and tea.

[EX Q]: Invaluable intuitively seems to imply a higher degree of importance. Please explain the difference between valuable and invaluable and in what context you'd use one or the other.
[EX A]:
Technically, invaluable works like priceless. They mean that something is of a value which cannot be expressed in numbers. For example great memories, happiness, health, or whatever else you prefer. They are invaluable, because they cannot be sold or bought. They have no price. On the other hand, valuable means something is of a high value, which can be expressed in numbers. Like a golden ring. It's valuable, because it costs $1000.