Basic Roots:
* auto-: self (autobiography, automatic, autonomy)
* bio-: life (biology, biosphere, biopsy)
* cosm-: world, universe (cosmos, cosmopolitan, microcosm)
* geo-: earth (geography, geology, geocentric)
* graph-: write (graphic, autograph, photograph)
* helio-: sun (heliocentric, heliotrope, helium)
* hydro-: water (hydroelectric, hydrant, hydrophobia)
* logy-: study of (biology, geology, psychology)
* meter-: measure (diameter, thermometer, kilometer)
* micro-: small (microscope, microorganism, microphone)
* morph-: form, shape (morphology, metamorphosis, amorphous)
* path-: feeling, suffering (empathy, apathy, pathology)
* phone-: sound (telephone, symphony, microphone)
* photo-: light (photograph, photogenic, photosynthesis)
* poly-: many (polygraph, polygon, polyglot)
* scope-: look, see (telescope, microscope, periscope)
* tele-: far (telephone, television, telegraph)
* thermo-: heat (thermometer, thermostat, thermal)
More Complex Roots:
* anthrop-: human (anthropology, misanthrope, philanthropy)
* arch-: ruler, chief (monarch, hierarchy, archive)
* chron-: time (chronology, synchronize, chronicle)
* demo-: people (democracy, demography, demagogue)
* ethn-: nation, people (ethnicity, ethnography, ethnocentric)
* gam-: marriage (monogamy, bigamy, polygamy)
* gen-: birth, origin (genesis, genealogy, congenital)
* graph-: write (autograph, telegraph, biography)
* hetero-: different (heterogeneous, heterosexual, heterodox)
* homo-: same (homogenous, homosexual, homophone)
* lith-: stone (lithography, monolith, megalith)
* log-: word, speech (dialogue, monologue, eulogy)
* mega-: large (megaphone, megaton, megastar)
* morph-: form, shape (metamorphosis, amorphous, morphology)
* nym-: name (anonymity, pseudonym, synonym)
* path-: feeling, suffering (sympathy, apathy, pathology)
* phil-: love (philosophy, philanthropy, bibliophile)
* soph-: wisdom (sophist, philosophy, sophisticated)
Important Note:
These are just a few examples, and many more Greek roots exist! By learning some of these basic roots, you can often decipher the meanings of unfamiliar words.