TASK DEFINITION: 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.
PROBLEM: I would like to use a noun made of multiple words (like particle board, Mount Everest, or windscreen wiper) in a compound adjective with a hyphen. But I don't know how to hyphenate such a composition. I'm not sure how common this situation is, so here's an example: Machine learning is a single noun made of two words, and I want to use it in a compound adjective with a hyphen. Are either of the following examples correct? I would like to pursue a machine learning-related certification. I would like to pursue a machine-learning-related certification. If not, then what is the correct way to hyphenate compound adjectives like this?.

SOLUTION: Bryan Garner, Garner's Modern American Usage (2003) has a useful discussion of this problem in his lengthy coverage of phrasal adjectives: E. The Compound Conundrum. When the first or last element in a phrasal adjective is part of a compound noun, it too needs to be hyphenated: post-cold-war norms, not post-cold war norms. Otherwise, as in that example, cold appears more closely related to post than to war. In your example, machine learning is the compound noun and related is the additional element in the adjective phrase, so Garner would endorse punctuating it as machine-learning-related. The Chicago Manual of Style, fifteenth edition (2003) takes essentially the same position as Garner: 5.92 Phrasal adjectives. A phrasal adjective (also called a compound modifier) is a phrase that functions as a unit to modify a noun. A phrasal adjective follows these basic rules: ... (2) If a compound noun is an element of a phrasal adjective, the entire compound noun must be hyphenated to clarify the relationship among the words {video-game-magazine dispute} {college-football-halftime controversy}. Words Into Type, third edition (1974) emphasizes the practical goal to be achieved by hyphenating (or not hyphenating): Phrases used as attributive adjectives usually require hyphenation to make clear their relation to the noun they modify. [Examples:] the how-to-study area; a life-and-death struggle If such a phrase modifier is hyphenated at all, it should be hyphenated throughout; but no hyphen should be used between the modifier and the noun. Wrong: low milk-and-cream yielding dam Right: low milk-and-cream-yielding dam Wrong: pay-as-you-go-plan Right: pay-as-you-go plan If there is scarcely any possibility of misreading, hyphens need not be used. [Examples:] a story and a half house; a thirty percent increase; yellow pine timber belt All of these (U.S.) style guides agree that when ambiguity as to what is modifying what might ensue from an unpunctuated adjective phrase, it is better to hyphenate the elements of the phrase than to leave the words open. But the goal is greater clarityand if the hyphens don't clarify anything, they have no business being there. Thus far, my answer has focused on the 'machine-learning-related certification' example in your question. Compound modifiers that incorporate proper nouns of two words or more (such as 'Mount Everestbased climbing expedition') follow a different rule in these style guides: leaving the proper name open, and connecting the compound noun to the adjective with an en-dash instead of a hyphen. I won't go back into the reference works to quote the specific guidelines from each book, but they recommend the approach I have just outlined in this paragraph.

PROBLEM: When you are writing about the seasons, should you capitalize their names? For example, would you say: I love the colors of the leaves in Autumn. Or should you say: I love the colors of the leaves in autumn.

SOLUTION: The names of seasons should be left uncapitalized. However capitalization may be used to achieve a poetic effect.

PROBLEM: 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.

SOLUTION:
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.