The Differences Between L and R in English

phonemes are abstractions of speech sounds they're not the sounds themselves. What constitutes a phoneme depends on the particular language and differs from one language to another. A single phoneme can be pronounced in lots of different ways whereas a single phonetic unit is pronounced in exactly one way. Phrases change over time so we need to look at how these changes have been made as part of historical linguistics. So there's sort of things that phonologists would study such as minimal pairs or other types of distinctions between words, for example F and V used to be considered part of the same phoneme but then later came to be distinguished by their own characteristics.