Here’s the Wikipedia entry on phonemes:
In your first post, you used both the terms “phoneme” and “phone” as if they were synonymous. They aren’t. A phone is the way a phoneme is pronounced in a particular context in a language. A phoneme is anything that is contrasts minimally with another phoneme. English speakers consider that, say, the words “choo,” “zoo,” “Sue,” “Jew,” “Lou,” “goo,” and “two” contrast minimally. No native English speaker, if asked to drop the first sound in “choo” or “zoo” would say that “shoe” or “zhue” would be left. They would say that “oo” is left, just as they would say that that is what’s left if you dropped the first sound in “Sue,” “Jew,” “Lou,” “goo,” or “two.” The definition of a phoneme depends on the native speaker’s feeling for the language, not the phonetic reality.