Pronunciation: /ˈpɛ-trɪ-kɔr/ Part of speech: noun Definition: The distinctive, earthy, and usually pleasant scent produced when rain falls on warm, dry soil. Etymology: The word was coined in 1964 by Australian mineral chemists Isabel Joy Bear and Richard Grenfell Thomas, who introduced it in a paper published in the journal *Nature*. It is compounded from Ancient Greek *petra* (πέτρα), meaning "rock" or "stone," and *īchōr* (ἰχώρ), the ethereal fluid believed to flow through the veins of the gods in Greek mythology. The science behind it: raindrops interact with geosmin and volatile plant oils in dry soil, releasing the compounds into the air. Synonyms: argillaceous odor, rain scent, earth-smell, pluvial fragrance, geosmin aroma, rain perfume In a sentence: She stepped onto the porch as the first drops hit the flagstones, breathing in the petrichor_ that rose from weeks of sun-baked earth.