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: Is the word 'Customizable' a valid English word? Every time I write that word, the spell checker underlines it, and it suggests using 'Customization' or 'Customize'. I'm not a native English speaker, but that word exists in online dictionaries so I wonder why the spell checker underlines it.
Example Output: The Oxford English Dictionary in its revision of March 2012 defines it as: That may be customized; able to be changed to suit the requirements of the user. Frequently with reference to computer software and hardware. The earliest citation is from 1960. If that definition of customizable suits your purpose, then there's no reason why you shouldn't use it.

Example Input: How should you reply to 'what's up?'.
Example Output: 'What's up' means 'What's happening.' I usually just reply 'nothing.' because nothing is happening to me. But, there are alternatives, such as the usual reply to a greeting: Not much Nothing. Yourself? I'm good, yourself? Good. How are you? However, if there is something that you would like to tell the other person e.g. You've sold your car, it might go like this: A: What's up? B: I've sold my car. A: Good on you mate!

Example Input: Upon answering the telephone, the person calling asks if Joan is available. If Joan is the person who answered the phone, should she say 'This is her' or 'This is she'?.
Example Output:
Traditional grammarians prefer the nominative ('she') for the complement of the verb 'to be'. Most usage in my experience prefers the accusative ('her') and regards the verb as having a direct object rather than a complement. I suspect the traditional grammarians, as they often did, have misapplied a rule of Latin grammar. In Latin, 'esse' takes a complement in the nominative case, but Latin declines the verb strongly enough that it doesn't bother with a pronoun as the subject of a verb unless needed for emphasis. 'It is she' in Latin would be 'illa id est', which looks far more natural than the English. Note that it's 'c'est lui' in French, so there isn't a general rule for a complement of 'to be' being in the nominative. Explanation: A normal (transitive) verb, like say 'have' has a direct object, which is in the accusative case. So, for example, 'I have her' uses 'her' as a direct object, and 'her' is in the accusative case, where 'she' is in the nominative case. In Latin, the verb 'esse' ('to be') is special; it doesn't have a direct object in the accusative case, it has a complement in the nominative case. English grammarians in the eighteenth and nineteenth centuries adopted a number of rules of Latin grammar into English; this was one of them. In Latin, 'it is she' and 'she is it' are both the same thing 'id illa est' or 'illa id est' can both be translated either way - the point being that the 'is' ('est') just equates to things to each other - it's like in maths you can have x=y or y=x and they both mean the same thing. English, though, takes word-order very seriously, and a pronoun after a verb is very strongly marked as being in the objective case and you don't get the benefit that you get in Latin from the exception - there's still one before the verb and one after; you don't get to make clear that it's commutative. So you have a special-case for a verb, which you get no useful benefit from. It's hardly surprising that most English speakers have reverted to 'it is her' rather than 'it is she'. A note on cases: Latin is conventionally described as having seven cases (though only five are actually different for most nouns and pronouns). It has two cases, accusative and dative for the objects of verbs. English's residual case system only has the one case for both, which merge into the objective case (in fact, a third Latin case, ablative, merges in too). That's why the two paragraphs above appear to use two different words for the same case.

