Why does ph say f?

Why is the word phonetically not spelled the way it sounds (starting with an "f")? 

The letter combination "ph" sounds like "f" because of the influence of Ancient Greek on the English language. In Ancient Greek, the letter "phi" (Φ) was originally pronounced as an aspirated "p" (/pʰ/), which sounds like a regular "p" followed by a burst of air, similar to the "p" in the English word pot.

Over time, during the Koine Greek period (around the 4th century CE), the pronunciation of "phi" shifted to the "f" sound (/f/). However, when the Romans borrowed Greek words into Latin, they represented "phi" with the combination "ph" to approximate the original aspirated "p" sound. English later inherited these words and spellings from Latin, which is why we now write "ph" even though we pronounce it as "f."

For example, the English word phonetic comes from the Greek word φωνητικός (phōnētikos), meaning "pertaining to sound." In Classical Greek, this word would have been pronounced approximately as pʰōnētikos, but by the time English adopted the word, the "ph" was pronounced as "f," and the spelling from Latin was retained.

This blending of Greek and Latin influences explains why so many English words of Greek origin, like phone, photograph, and philosophy, have "ph" pronounced as "f."