Phone. Phase. Phoenix. These words start with a “ph”, yet this digraph is pronounced with an “f”. In some other languages, we see such a pattern as well. Take French, for example. The word for “the seal”, le phoque, also has its “ph” pronounced as an “f”. We also see such a pattern in Vietnamese, which uses the Chữ Quốc ngữ, a Latin alphabet based on the Romance languages. For instance, the Vietnamese word for the “French langauge” is Tiếng Pháp, and the “ph” is also pronounced as an “f”.
Noticing this pattern between writing and sound, we have to ask ourselves these questions — Has is always been this way, and why?
For some languages, this is not always the case. For instance, Middle Vietnamese realised “ph” as [pʰ], also known as an aspirated “p”. However, this was around the time a different writing system was used — the logographic Chữ Nôm, and so we might not have seen such a transliteration as we do in Chữ Quốc ngữ today.
Going further back in time, in the context of some European languages like English and French, many of these words with “ph” in them ultimately trace back to Greek words. Perhaps that is where some sort of sound changes would have occurred. Right?
Firstly, let us take a look at Latin. Latin had a rather sizeable inventory of loanwords of Greek origin. These Greek words had this letter known as phi, or φ, which were transcribed in Latin to be “ph”. This was the source of many of these “ph” digraphs that are realised with the “f” sound. Words like phonetics, phone, phonology, philosophy, and even our good old French words like phoque. However, native Latin words carrying the “f” sound are written with “f”. So why the “ph”?
But here is the kicker. When the “ph” entered use in Latin, neither Latin nor Greek realised this (nor phi) as an “f” sound. Instead, it was a sound we have mentioned before — the aspirated “p” sound, or [pʰ]. Over time, this sound softened to a “f” sound. This change may have started in Greek, and was later matched in Latin. However, people decided not to change the way it is written in Latin, leaving two primary ways of transcribing the “f” sound — as letter “f”, or the digraph “ph”. The latter still distinguished the word’s Greek origins, and applied largely to Latin words of Greek origins. As Latin further diversified into the Romance languages, this orthography still persisted. And as French words entered English, the way we write words like “philosophy” was generally conserved (for the “ph” part), hardly ever written as “filosofy” other than the cases of misspelling.
It must also be noted that each language had its own subsequent sound changes thereafter. For instance, there is the Grimm’s Law that was put forward for sound changes from Proto-Indo-European roots to Proto-Germanic, to Germanic languages. One of these sound changes (or shifts) is the *p > f [ɸ]. But this is not really the source of the “ph” being pronounced as “f”, since it could have occurred around the time Latin and the Germanic languages coexisted, or perhaps earlier.
To conclude, the digraph “ph” is a reminder of the word’s history and origin, as we trace back their roots to Greek. It represents a bunch of sound changes that have occurred in the languages that birthed these words, and how this system pretty much went untouched for a significant portion of the written histories of languages like French. Its influence could be felt as far east as Vietnam, as it replaced the Chữ Nôm with the Chữ Quốc ngữ, under the influence of Romance languages. It seems like an unusual way to transcribe an “f” sound, but behind it, lies so much of history.