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]: In math, we use the term series a lot, and there are many types of series. How should I craft my sentence when I have three different ones in mind to talk about? Should I settle down for a less mortal alternative of 'list of series' or something like that? The existing question on The possessive and plural forms of 'series' suggests the usage of series'. But is that all? If that's the only solution, then could you please explain the usage of apostrophe symbol at the end? Is that a plural marker or a possessive marker, or both?.
[EX A]: Series (like deer, salmon, and sheep) is pronounced and spelled the same in the plural as in the singular. If either the singular or the plural is used as a possessive, an apostrophe is added to show that in print, though there is no pronunciation difference in speech. Thus, The series doesn't converge. (singular) The series don't converge. (plural) This series' limit is unknown. (singular possessive) These series' limits are unknown. (plural possessive) More examples can be seen here.

[EX Q]: Does the letter 'C' make any sound that cannot be made by other letters? 'Cat' could be spelled 'Kat,' 'Cinder' could be spelled 'Sinder,' and 'Watch' could be spelled 'Watsh.' Edit: An excerpt from a comment by Kosmonaut: There is no difference between ['ch' and 'tch']; both are /t/. Thus, 'witch' and 'which' are pronounced exactly the same: [wt]. (Actually some Southern American dialects pronounce 'which' as [t], but that is only a difference in the 'w' sound, not the /t/.).
[EX A]: This is not a bad remark. All Germanic cognates of cat are indeed spelled with a 'k' (from P.Gmc. *kattuz, O.Fris. katte, O.N. kottr, Du. kat, O.H.G. kazza, Ger. Katze). The English word is spelled with a 'c' under the influence of Late Latin (cattus). See step 3 below. All Germanic cognates of cinder are indeed spelled with an 's': P.Gmc. *sindran (cf. O.S. sinder, O.N. sindr, M.L.G., M.Du. sinder, O.H.G. sintar, Ger. Sinter. Initial s- changed to c- under influence of Fr. cendre 'ashes. See step 4 below. The letter 'C' has already disappeared from a lot of words. Here are a few examples of the evolution of the spelling of some Old English words. queen used to be spelled cwen (and mean 'young woman'). quick used to be spelled cwic (and mean alive). drink used to be spelled drinc. bishop used to be spelled biscop (closer to 'Episcopal'). ship used to be spelled scip. Of course there is no single cause to all these changes. And even summarising them in a small answer is a huge challenge. But there is an interesting section in the wikipedia article about the 'C' letter. Yet I'd like to add a few background considerations. After the Anglo Saxon conquest of Britain in the 5th century, texts (very few have actually come down to us) were all written in the Runic Alphabet, because that was the alphabet in use in Germany (it had actually been borrowed from the Etruscan who add taken it from the Greeks who... who... Proto-Canaanite/Egyptians). In other words the Latin alphabet introduced by the Roman occupation fell into complete oblivion. When Pope Gregory sent out Augustine to convert the famously 'non angli, sed angeli' heathens, the dominant writing system shifted back to the Latin alphabet. Within a few decades England quickly raised to the most culturally prominent country in Europe (its lavishly illuminated Bibles and other religious manuscripts can still be found in many European museums and libraries). But the language used for these masterpieces was still Latin. There are very few words of English in these texts. Then the Vikings raided the monasteries to plunder all their riches and in the process they killed a large proportion of scholars. As a result, when King lfred endeavoured to rekindle the light of English culture, he started writing texts in 'Old nglisc' instead of Latin. For this purpose he naturally used the Latin alphabet with however the addition of a few runic characters (among which the '' and the '' for the sound 'th'). The 'c' was used for the sound /k/, 'cw' for /kw/ (queen), 'ce' and 'ci' for [t] (child) and 'sc' for [] (ship). These conventions were inspired from Vulgar Latin. In Middle English (in the wake of the Norman invasion), under the influence of the French spelling system, English underwent a spelling reform which affected many words containing the letter 'c'.

[EX Q]: I want to tell my uncle that I am 'f***ing around' but I certainly can't use the F word. I googled it but I didn't find the phrase/word I am looking for. I am wasting my time doing silly things and I want a phrase or word for that. Can anyone give any formal or polite phrase for that?.
[EX A]:
I want to tell my uncle that I am 'f***ing around' but I certainly can't use the F (f*ck) word. If you don't want to say 'f*ck' then say fiddle instead. Both 'fck' and 'fiddle' start with F, so 'fck' can easily be replaced by 'fiddle'. Fiddle around: To spend time doing small things that are not important or necessary Cambridge English dictionary You could substitute 'fiddle' for 'f*ck'. Example: Uncle, I'm fiddling around. (It does not sound vulgar). Single word for that would be loafing. Loaf (verb): Spend one's time in an aimless, idle way. Lexico Example: Uncle, I'm loafing. Or footle. But as others have said, it's unlikely to be understood. Footle (verb): Engage in fruitless activity; mess about. Lexico