Concept
In phonology, liquids are a class of consonants consisting of voiced lateral approximants like /l/ together with rhotics like /r/. The grammarian Dionysius Thrax used the Ancient Greek word ὑγρός (, ) to describe the sonorant consonants (/l, r, m, n/) of classical Greek. Most commentators assume that this referred to their "slippery" effect on meter in classical Greek verse when they occur as the second member of a consonant cluster. This word was calqued into Latin as liquidus, whence it has been retained in the Western European phonetic tradition. Liquids as a class often behave in a similar way in the phonotactics of a language: for example, they often have the greatest freedom in occurring in consonant clusters. Cross-linguistically, liquids are the consonants most prone to metathesis. In Spanish, /r/ is liable for metathesis. More specifically, /r/ and /l/ frequently switch places: Lat. crocodīlus > Span. cocodrilo “crocodile” Lat. mīrāculum > Span. milagro “miracle” Lat. perīculum > Span. peligro “danger” Lat. parabola > Span. palabra “speech” comfortable is frequently pronounced /ˈkʌmf.tɚ.bəl/ in rhotic varieties, although its stem, comfort is pronounced /ˈkʌm.fɚt/, with the rhotic /ɹ/ in its original position. Liquids are also prone to dissimilation when they occur in sequence. Latin peregrinus > Old French pelegrin (> ) Italian colonello > Middle French coronnel This example of a relatively old case of phonetic dissimilation has been artificially undone in the spelling of English colonel, whose standard pronunciation is /ˈkɝnəl/ (with the r sound) in North-American English, or /ˈkɜːnəl/ in RP. It was formerly spelt coronel and is a borrowing from Middle French coronnel, which arose as a result of dissimilation from Italian colonnello. Liquids are also the consonants most prone to occupying the nucleus slot in a syllable (the slot usually assigned to vowels). Thus Czech and other Slavic languages allow their liquid consonants /l/ and /r/ to be the center of their syllables – as witnessed by the classic tonguetwister strč prst skrz krk "push (your) finger through (your) throat".