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.

Coming from a technical background I'm slightly confused. What is the difference between simultaneously and concurrently? How do we use these words?.
I just looked these up in an online dictionary; this is what I found: concurrently: overlapping in duration simultaneously: at the same instant Both of them mean 'at the same time,' and are almost interchangeable. That said, if I had to point out a slight difference, I'd say that concurrently occurs over a longer time, and is a bit less synchronized than simultaneously. For example: The two processors were running concurrently, then they crashed simultaneously. In that example, I wouldn't swap the two words in question.

I'm struggling to recall this word. If I recall correctly, it's of French origin. My search has so far been fruitless. The nearest equivalent I came up with was the idiom pulling strings but that is obviously English and not a single word. pull strings / wires (a) to use one's influence or authority, usually in secret, in order to bring about a desired result. (b) to gain or attempt to gain one's objectives by means of influential friends, associates, etc.: He had his uncle pull strings to get him a promotion.
sinecure: sinecure (sini-kyoor, sini-) n. A position or office that requires little or no work but provides a salary. n. Archaic An ecclesiastical benefice not attached to the spiritual duties of a parish. More at Wordnik from The American Heritage® Dictionary of the English Language, 4th Edition

I'm referring to the peculiar habit I sometimes see in formal documents, where a number is given numerically after it's spelled out. It seems quite redundant: I need five (5) kumquats, stat! (Though it isn't always in a legal context, might it be related to this answer on this question?).

The redundancy is presumably intended to reduce typos, forgery, and other types of error or manipulation in order to make the intent as clear as possible. It is known professionally as a CYA. It's obvious what my intent is when I rather carelessly write an I.O.U. for sevum kumquats, but alas, sevum is not really a word and opens up our contract to litigation. Adding the numeral 7 in parenthesis after sevum clarifies the intent. Similarly, if I were to write an I.O.U. for 3 kumquats, one could easily change that 3 to an 8, but it is far more difficult to make three look like eight. The practice appears to be a legal tradition rather than a universally honored rule. If you've ever written a check (known as a cheque to the Queen), you've written out a number with words and followed it with a numeral (albeit without parenthesis).