ge·ol·o·gy 
(jē-ŏlə-jē)
(jē-ŏlə-jē)n. pl. ge·ol·o·gies
1. The scientific study of the origin, history, and structure of the earth.
2. The structure of a specific region of the earth's crust.
3. A book on geology.
4. The scientific study of the origin, history, and structure of the solid matter of a celestial body.
[Medieval Latin geōlogia, study of earthly things : Greek geō-, geo- + Greek -logiā, -logy.]
ge′o·logic (jē′ə-lŏjĭk), ge′o·logi·cal adj.
ge′o·logi·cal·ly adv.
ge·olo·gist n.