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.
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Question: What is the correct version of this common phrase? First come, first serve First come, first served Gramatically, I believe 2. is the correct form. However, it seems that 1. is commonly employed in spoken and even written English.

Answer: The second is correct. It is a form of 'Those who come first are served first.'


Question: Is there a specific reason for this? After all, it is 'boys and girls', rather than 'girls and boys'. If the boy (male) comes first here, why doesn't it come first in 'ladies and gentlemen'?.

Answer: It probably has to do with the phonetic and metrical properties of 'ladies and gentlemen' versus 'gentlemen and ladies.' Say them both out loud and see which one sounds better to you, intuitively. The metrical pattern of 'ladies and gentlemen' consists of (arguably) two dactyls. A dactyl is a group of three syllables where the first is stressed and the second two are unstressed. When these occur in succession, they are pleasant to the ear. ladies and gentlemen DUM da da / DUM da da The metrical pattern of 'gentlemen and ladies' falls into a much less regular pattern. It is less pleasant to the ear. It is something like a stressed syllable followed by three unstressed syllables followed by a stressed syllable followed by an unstressed syllable. gentlemen and ladies DUM da da da DUM da Our language tends to organize itself according to regular and pleasant stress patterns. My guess is that is why we feel more drawn to 'ladies and gentlemen' than 'gentlemen and ladies' and why the former has conventionalized.


Question: What's an antonym for 'virgin'? A single word would be preferable.

Answer:
This is OP's second question on EL&U, and the previous one refers to the fact that he's 'writing an application that deals with blind studies'. In light of that, I assume OP is effectively looking for a medical term. I'm not a doctor, but these people are, and they use the term coitally experienced. Here's an NGram showing they're not alone. In case anyone objects that (besides not being single-word) coitally experienced applies to males as well as females, I suggest post-coitarchal or perhaps my own neologism coitarchated (which I think would be well enough understood on first encounter by people working in that area). Coitarche (first experience of full intercourse) didn't really enter the lexicon until the early '80s, but it's clearly formed by association with menarche (a pubescent girl's first period), so I think that's good enough to say coitarche and derivatives relate more to the female than the male side of the experience.