When you know the meaning of English words ending in -logy, then you know more Greek words than you think. The first compound of English words ending in -logy is also a Greek word. For instance, from cosmo-logy you know the Greek word κόσμος, the world, the people, from theo-logy you know Θεός, the God, from ecclesiology you know εκκλησία, the church, from hematology you know αίμα, the blood, from gynecology you know γυναίκα, the woman, from neurology you know νεύρα, the nerves, from ethnology you know the word έθνος, the nation etc.

The suffix -logy, λογία in Greek, comes from the word λόγος. Λόγος is the Greek word that is most often used in English as a component of compound words. Ο λόγος means the verbal expression, the speech and the reason as well. In ancient Greek it additionally meant the logic, the rational thinking implying the direct connection between talking, reasoning and rational thinking in ancient Greek culture. Consequently, the suffix -λογία, -logy, which occurs in English words, means the science.

WORD CLUSTERS
English word Greek word Pronunciation
Anthropology η ανθρωπολογία EE anthropoloYEEa
Human, man ο άνθρωπος O Anthropos
Archaeology η αρχαιολογία EE arheoloYEEa
Ancient o αρχαίος, -α, -ο O arHEos, -a, -o
Antiquities τα αρχαία TA arHEa
Astrology η αστρολογία EE astroloYEEa
The star το άστρο, το αστέρι TO Astro, TO aSTEri
The stars τα άστρα, τα αστέρια TA Astra, TA aSTEria
Bacteriology η βακτηριολογία EE vaktirioloYEEa
Bacterium το βακτήριο, -α TO vakTEErio, -a
Climatology η κλιματολογία EE klimatoloYEEa
Climate το κλίμα TO KLEEma
Meteorology η μετεωρολογία EE meteoroloYEEa
Meteor ο μετεωρίτης O meteoREEtis
Dermatology η δερματολογία EE dermatoloYEEa
Skin το δέρμα TO DErma
Geology η γεωλογία EE yeoloYEEa
The earth η γη EE YEE
Cosmology η κοσμολογία EE kosmoloYEEa
Cosmos ο κόσμος O KOsmos
Ecclesiology η εκκλησιολογία EE eklisioloYEEa
Church η εκκλησία EE ekliSEEa
Theology η θεολογία Ee theoloYEEa
God ο θεός O theOS
Ecology η οικολογία EE ikoloYEEa
House ο οίκος O EEkos
Ethnology η εθνολογία EE ethnoloYEEa
Nation το έθνος TO Ethnos
Gynecology η γυναικολογία EE yinekoloYEEa
The woman, wife η γυναίκα EE yiNEka
Neurology η νευρολογία EE nevroloYEEa
The nerve το νεύρο TO NEvro
The nerves τα νεύρα TA NEvra
Hematology η αιματολογία EE ematoloYEEa
Blood το αίμα TO Ema
Gerontology η γεροντολογία EE yerontoloYEEa
Old man ο γέροντας, ο γέρος O YErontas, O YEros
Old woman η γριά EE yriA
Graphology η γραφολογία EE yrapholoYEEa
I write γράφω YRApho
Microbio+logy η μικροβιο+λογία EE mikrovioloYEEa
small ο μικρός, -ή, -ό O miKROS, -EE, -O
the life ο βίος O VEEos
microbe το μικρόβιο TO miKROvio
Zoology η ζωολογία EE zooloYEEa
The animal το ζώο TO ZOo
The animals τα ζώα TA ZOa
The life Η ζωή EE zoEE
Speleology η σπηλαιολογία EE spileoloYEEa
The cave η σπηλιά EE spiliA
Seismology η σεισμολογία EE sismoloYEEa
Earthquake ο σεισμός O siSMOS
Earthquakes σεισμούς siSMOOS (Acc. Plural)
Musicology η μουσικολογία EE moosikoloYEEa
Music η μουσική EE moosiKEE

THE SUFFIX -LOGIST IS -ΛΟΓΟΣ
You know many more than these words. The suffix -logist indicates the specialist engaged in the study of something. Just add this ending instead of -logy in the above words and you name him: ethnologist, gynecologist, neurologist etc. In Greek you just add the suffix -λόγος: ανθρωπολόγος, εθνολόγος, αρχαιολόγος, θεολόγος, μουσικολόγος, γεωλόγος, σεισμολόγος, σπηλαιολόγος, αστρολόγος, γυναικολόγος, μικροβιολόγος, νευρολόγος, δερματολόγος, γεροντολόγος, κλιματολόγος, μετεωρολόγος, εκκλησιολόγος.
PRONUNCIATION KEY
i (idiom), ee (bee), e (energy), o (organism), oo (boot), y (yes), h (helium), th (theory), d (the). The capitalized syllables are accented.