溝

ditch

gutter

oceanic trench

Japan Trench

multipurpose underground utility conduit

Japanese night heron (Gorsachius goisagi)

drainage ditch

large ditch

lateral sulcus (brain structure)

rift valley

gutter oil

ditch water

Mariana Trench (deepest part of the ocean, near the Mariana Islands)

U-shaped gutter

L-shaped gutter

sulcus

Japanese bird cherry (Prunus grayana)

Marco Polo Bridge Incident (July 7, 1937)

trench digging machine

groove in the body of wooden plane which holds the blade

fluting

channel (type of section steel)

fissured tongue

clearance groove

epidermal depression

gingival sulcus

subterranean drain

Marco Polo Bridge (China)

mammary slit (e.g. in whales and dolphins)

Solenogastres (subclass of small worm-like molluscs)

Chinese lobelia (Lobelia chinensis)

plant native to eastern Russia and Hokkaido (Mimulus sessilifolius Maxim. p)

record groove

grooved rail

cleaning out mud from a ditch or drain

keyway

brown rat (Rattus norvegicus)

ditch mud

Chinese pond mussel (Sinanodonta woodiana)

drainage

bird cherry (Prunus padus)

nasolabial sulcus

monkey flower (plant)

furrow ridges

Sphaerium japonicum (species of fingernail clam)

drain and pool for collecting sewage, etc.

ditch