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.

Example Input: Are both is equal to and equals similar in meaning? Which is the more natural? For example, one plus one equals two or one plus one is equal to two.
Example Output: Both are grammatically correct and mean the same. And both are the natural ways of saying it. Use either.

Example Input: What should be your response when your boss thanks you for using his own resource allotted to you and you respect your boss and cannot respond him like It's ok or you're welcome.
Example Output: Some appropriate responses would be: 'My pleasure.' 'Don't mention it.' 'You're [most] welcome.' 'I'm glad I could help/be of help.' 'Oh [no], thank you! Always at your service.' 'It was not a problem at all. [I'm] glad I could be of assistance.' And, of course, you could use 'sir' or 'ma'am' to make your response even more polite.

Example Input: Somehow I am compelled to use the word 'metal' to describe strong 'intestinal fortitude', and perseverance however I can't find the spelling or any synonym like this. Does a word that sounds like 'metal' exist when describing an individual's character? I'm looking for modern or historic usage of the word.
Example Output:
Mettle Defined by Oxford Dictionaries as: a person's ability to cope well with difficulties; spirit and resilience. It is commonly seen in the phrase: (put someone) on their mettle meaning, (of a demanding situation) test someone's ability to face difficulties. 'there were regular public meetings where local MPs were put on their mettle and remorselessly pilloried' Source: ODO Other constructions are possible too, for example: test their mettle, apparently an American version (thanks, @PeterCordes) show your mettle, etc. Origins According to Merriam-Webster, mettle was, as @Sparhawk points out in the comments, originally simply a variant spelling of the word metal (which dates to at least the 13th century), and it was used in all of the same senses as its metallic relative. Over time, however, mettle came to be used mainly in figurative senses referring to the quality of someone's character, with a first known usage in 1581. Today, both words can mean 'vigor and strength of spirit or temperament,' but only metal is used of metallic substances.

