Meaning

noun the branch of geology that studies rocks: their origin and formation and mineral composition and classification

originEtymology tree Ancient Greek πέτρᾱ (pétrā)bor. Latin petrader. English petro- Proto-Indo-European *leǵ- Ancient Greek λόγος (lógos) Proto-Indo-European *-h₂ Proto-Indo-European *-éh₂ Proto-Indo-European *-i-eh₂ Proto-Hellenic *-íā Ancient Greek -ῐ́ᾱ (-ĭ́ā) Ancient Greek -λογῐ́ᾱ (-logĭ́ā)bor. Latin -logialbor. French -logiebor. English -logy English petrology From petro- + -logy.

Etymology from Wiktionary, CC BY-SA 3.0