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]: English isn't my mother tongue, and when we recently talked to a native speaker (during some company audit), he pointed out that the plural word 'trainings' is actually wrong (he pointed that it is a very common mistake and was almost amused by it). I couldn't understand why and wondered what the correct plural of 'training' would be. Online Dictionaries/Thesaurus don't answer it, so it's probably another opinion-based statement. I haven't found a source to back it up, though.
[EX A]: Training is both countable and uncountable. Usually, referring to a process, it is uncountable and has no plural. It is sometimes used to mean 'a specific training event', and is then countable, and has the plural 'trainings'. The OED has examples of this use going back to 1578, with the plural recorded from 1598.

[EX Q]: So basically, I know the name for both sides of a coin, yet not the coin itself. In other words, when you refer to a coin, you don't want to say 'this object with one side heads, and the other tails', you would want to say 'this coin'. What I want is a general term to refer to two ideas, that are the absolute opposite to each other. I can't really use the word 'concept', or 'idea', because such words are already assigned to the very concepts/ideas themselves.
[EX A]: polar opposites: polar opposite (plural polar opposites): The complete opposite, opposite in every way. 'Polar opposites' might also refer to the scientific or technical definition of two things having exactly opposing or inverted polarity, sign, orientation, or some other property.

[EX Q]: The phrase 'I miss you' can be equivocal: suggestive of (a) romantic longing and/or (b) regret of loss. Certainly, context can shape its meaning, including geography, historical period, and the speakers and their relationships. Given the circumstances in which it would be desirable to eliminate ambiguity, such as a platonic friendship, is there an alternative phrase for expressing (b) without (a)?.
[EX A]:
Your absence has resulted in a sense of loss. (Pretty impersonal and somewhat morbid. I can picture this being said by some distant relative at a funeral.) It would be nice if you were here. (Flirtatious.) I miss your friendship. (Suggests that they used to be friends, but no longer are.) How about: I miss hanging out together. It's boring here without you. Things aren't the same when you're not around. When are you coming to visit me? The answer is highly subjective depending on how close the friendship is, the type of humor, how well 'they' know each other. What I mean by that is if they are very close and have a slightly naughty side they can get away with sexual connotations because they know their friendship will never go that way nor do they want it to (or at least one of them doesn't). I miss sleeping with you! (As in spending the night together for some reason, but not sex.) Did you replace me yet? (As in, did they find a new friend while you've been gone.) Remember the times when we'd... (Good for reminiscing.) I miss your ugly mug. (Old style for: I miss your face.)