Compounding & the -ο- Linking Vowel

Greek joins two words into one COMPOUND, and the seam is almost always a linking vowel -ο-. Take the STEM of the first word, add -ο-, then the second word: χαρτί (“paper”) + πετσέτα (“napkin/towel”) → χαρτο + πετσέτα → χαρτοπετσέτα (“paper napkin”); ζάχαρη (“sugar”) + νερό (“water”) → ζαχαρόνερο (“sugar-water”); αλάτι (“salt”) + νερό → αλατόνερο (“brine, salt-water”); ψωμί (“bread”) + τυρί (“cheese”) → ψωμοτύρι (“bread-and-cheese”). The pattern is noun + noun (or adjective + noun), and the meaning is usually transparent from the parts - a χαρτοπετσέτα is a πετσέτα made of χαρτί. Two things shift at the seam: the first word loses its ending to a bare stem (χαρτί → χαρτ-, ζάχαρη → ζαχαρ-) and the whole compound takes a SINGLE new stress, often landing on that -ό- link (ζαχαρόνερο, αλατόνερο). Reading a long unfamiliar word, split it at the -ο-: the two halves usually name its parts.