溝 - gutter, ditch, sewer

oceanic trench; deep-sea trench; deep

ditch; drain; gutter; trench

ditch; drain; gutter; trench

fluting; grooving

keyway

mammary slit (in whales, dolphins and porpoises)

10^32; hundred nonillion

rift valley

ditch water

grooved rail

Japanese bird cherry (Prunus grayana); Gray's bird cherry; Gray's chokecherry

epidermal depression; skin depression