There are many Greek suffixes and prefixes in scientific and medical English. Many of them use PH, from the Greek letter phi Φ, to spell the F-sound /f/. In this article, I will cover many of them. Science and medical students will see many more words using PH than ordinary people will.
Examples include: astrophysics, anglophone, acrophobia, halophile and so on. Astrophysics is the compound of astronomy + physics. An anglophone is anyone who speaks English: Anglo- (English) + -phone the Greek word for sound. Plants that are halophiles can grow in salt water: meaning halo- (salt) -phile (loving).
A special case: pH, meaning the relative acidity of water, needs a lower case p and a capital H. It is not related to the Greek phi.
The name of the country The Philippines comes from the Spanish Islas Filipinas, meaning "the islands of Philip," named for Philip II, king of Spain. After the end of Spanish colonial rule, one would have thought that they might have come up with their own name.
Some words with the PH spelling are not of Greek origin, but the PH spelling has been added to make them appear more sophisticated. For example the word phony (also phoney) is not of Greek origin, but comes from fawney, a gold plated brass ring sold as solid gold. Also the word cipher (also cypher) is originally from Arabic (by way of Spanish), not Greek.
To make everything easier to understand, I collected PH suffixes, prefixes and common roots together into a chart. Naturally, most examples are from science and medicine. The more common word forming parts are in bold.
Spelling note: In general for Greek suffixes ending in a vowel, that vowel is dropped when used with a root word that begins with a vowel. For example: The O in blepharo- is dropped in the word blepharitis. (see below)