Oasis
a fertile area that rises in a desert whenever water is regularly available
Wadis
a dry riverbed that fills with water when rare rain fall in a desert
Semiarid
having lower temperatures and cooler nights than hot, dry deserts
Vary
to show difference between things
Millenium
a period of a thousand years
Polytheism
the belied in more than one god
Monotheism
the belief in one god
Expand
to spread out; to grow larger
Collapse
a sudden failure, breakdown, or ruin
Hydropolitics
the politics surrounding water access and usage rights
Fossil water
water that fell as rain thousands of years ago and is now trapped deep below ground
Delta
an area where sand, silt, clay, or gravel is dropped at the mouth of a river
Silt
small particles of rich soil
Ergs
a large area of sand
Nomads
a person who lives by moving from place to place to follow and hunt herds of migration animals or lead herds of grazing animals to fresh pasture
Aquifer
an underground layer of rock through which water flows
Hieroglyphics
the system of writing that uses small pictures to represent sound or words
Caliph
the successor to Muhammad
Demonstrate
to show
Regime
a government