LOGOS

Logos! Now there's a word that's always intrigued me.
Its first three letters are LOGic, so I immediately thought that any word ending in logos, or logie in French and logy in English, had something to do with logic.
Now, LOGO is part of the Greek word logos, meaning speech, discourse, while the other Greek word LOGIA means theory. Interestingly, on one side we have discourse and on the other theory. What a marvellous language!

I can make an alphabetical list of words ending with this suffix and understand why. I'll name a few:

 

A)
ARCHAEOLOGY. Here archeo comes from the Greek 'arkhaios' meaning ancient and logos becomes science. Here we have a science that studies ancient civilizations, from prehistory to the Middle Ages, based on their material remains.

B)
BIOLOGY becomes the science of life, because BIO is a Greek word meaning LIFE.

C)
The same goes for COSMOLOGY, the science of COSMOS, but in reality,
COSMO comes from the Greek 'kosmos' meaning order or universe. So cosmology is a part of astronomy whose object is the study of the universe as a whole and its structure. Later we'll discover the cosmopolitan, the man who declares himself a citizen of the world, because 'polites' in Greek means citizen. Not to be confused with the Latin word 'politus' meaning cultivated, refined, elegant, which gave rise to the words polite and politeness.

D)
DEONTOLOGY, from the Greek word 'DEON' or 'DEONTOS'= duty+logy. Here we have the theory of moral duties and rights in the exercise of a profession.

I'll skip a few letters and get to

E) ONTOLOGY, a word I've always loved. Onto comes from the Greek 'ONTOS', meaning being, that which is. It's the knowledge of being as being, of being in itself.  In Latin, philosophy gives us ontologia, a line of reasoning that attempts to prove the existence of God. My research led me to discover Parmenides, the Greek philosopher whom Plato called "the Great".
According to him, being is an immobile continuum, and becoming is merely an appearance.
He is considered the father of ontology.

F) OPHTHALMOLOGY. From the Greek 'ophtalmo' meaning eye. This is the branch of medicine that deals with eye diseases. Several derivatives of this word have given OPHTALMIA, inflammatory disease of the eye, OPHTALMOMETER, optical instrument used to measure the radii of the curvature of the cornea.

G)
PSYCHOLOGY. Everyone thinks they know what this scientific study of psychic facts, these conscious and unconscious mental processes, is, but they forget that the word psyche, the totality of psychic phenomena that make up individuality, means soul in Greek.

Just now, I realized that I'd gone a little too far into the philosophical aspects of what I was saying, and I'm afraid I've, if not lost, at least drowned my reader.

I might add in conclusion that I've found a word with logo that's a prefix rather than a suffix.
I'm talking about LOGOMACHIE, which means 'argument about words'. MACHIE comes from the Greek 'makhé'= fight. And that explains it