-logy versus -ology
In English names for fields of study, the suffix -logy is most frequently found preceded by the euphonic connective vowel o so that the word ends in -ology. In these Greek words, the root is always a noun and -o- is the combining vowel for all declensions of Greek nouns. However, when new names for fields of study are coined in modern English, the formations ending in -logy almost always add an -o-, except when the root word ends in an "l" or a vowel, as in these exceptions: analogy, dekalogy, disanalogy, genealogy, genethlialogy, herbalogy (a variant of herbology), mammalogy, mineralogy, paralogy, petralogy (a variant of petrology); elogy; antilogy, festilogy; trilogy, tetralogy, pentalogy; palillogy, pyroballogy; dyslogy; eulogy; and brachylogy. Linguists sometimes jokingly refer to haplology as haplogy (subjecting the word haplology to the process of haplology itself).