Nature

Trou aux Cerfs

Trou aux Cerfs — Dormant volcanic crater in Curepipe, Mauritius

Trough

Trough: containers, low points, and scientific meanings

Turquoise

Turquoise: properties, history, uses, and varieties

Twilight

Twilight: dawn and dusk — causes, types, and practical importance

Typhoon Haiyan

Typhoon Tip

Typhoon Tip — record-setting 1979 Pacific super-typhoon

Umbilicus

Urethra

Urethra: anatomy, function, and clinical importance

Varve

Varve: annual sedimentary laminations and their significance

Vertical draft

Vertical draft (updrafts and downdrafts)

Water vapor

Water vapor: properties, formation, and role in weather and climate

Waterfowl hunting

Waterfowl hunting: practices, history, equipment, and conservation

Waves at shallow water

Weather front

Weather front: boundary between contrasting air masses

Weather map

Well

Whaling

Whaling: history, methods, and modern controversies

Whirlpool

Whirlwind

Whorl

Wilderness

Wildlife

Wind speed

Wing coupling

Winter

Wolong National Nature Reserve

Wolong National Nature Reserve (Sichuan, China)

Wood grain

Woodland

Wool

Wool: natural animal fibre, properties, production and uses

Yamato nadeshiko

Yellow

Yellow (color)

Yosemite Falls

Yosemite Falls — tallest waterfall in the United States