hy·dro·ge·ol·o·gy 
(hī′drō-jē-ŏlə-jē)
(hī′drō-jē-ŏlə-jē)n.
The branch of geology that deals with the occurrence, distribution, and effect of groundwater.
hy′dro·ge′o·logi·cal (-jē′ə-lŏjĭ-kəl), hy′dro·ge′o·logic adj.
hy′dro·ge·olo·gist n.
- fourhanded
- Four-H Club
- Four Horsemen of the Apocalypse
- Four Hundred
- Fourier
- Fourier analysis
- Fourierism
- Fourierist
- Fourierite
- Fourier series
- Fourier transform
- four-in-hand
- four-leaf clover
- four-letter word
- four-o'clock
- four-peat
- fourpenny nail
- fourplex
- four-poster
- fourragère
- fourscore
- foursome
- foursquare
- foursquarely
- four-star