The spelling of the phrase "stays in" is relatively simple, but understanding its pronunciation requires knowledge of IPA phonetic transcription. In IPA, "stay" is spelled /steɪ/, with the long "a" sound represented by the symbol "ɛɪ". "In" is spelled /ɪn/, with the short "i" sound represented by the symbol "ɪ". When the two words are combined, the pronunciation becomes /steɪz ɪn/, with the "z" sound representing the consonant blend of the two words. Thus, the spelling of "stays in" reflects its pronunciation in IPA.
The phrase "stays in" does not have its own distinct etymology, as it is formed by combining two separate words: "stays" and "in".
The word "stays" has several meanings and origins depending on the context. In this case, one can assume that "stays" refers to the verb form of the word, which means to remain or continue in a particular position or state. This sense of the word originated from Middle English and Old French, ultimately deriving from the Latin word "stare" meaning "to stand".
The word "in" is a preposition that primarily denotes location or position within something. It evolved from the Old English word "innan" and can be traced back to the Proto-Germanic word "innan" as well.
So, when combined together, the phrase "stays in" generally means to remain or continue inside or within a particular place or condition.