Color

1. Color
2. Black
3. White
4. Blue
5. Green
6. Red
7. Yellow

Tools

1. Drawing
   1. Pencil
   2. Pen
   3. Chalk
2. Painting
   1. Paint

Music

1. Music
2. Jazz
3. Songs

Musical instruments

1. Violin
2. Piano
3. Drum
4. Flute

Theater, Dance

1. Dance
   1. Salsa
   2. Tango
2. Theatre

Artists

1. Francisco Goya
2. Hokusai
3. Henri Matisse
4. Michelangelo
5. Leonardo da Vinci
6. Rembrandt

Authors

1. Aristophanes
2. Miguel de Cervantes
3. Brothers Grimm
4. Homer
5. William Shakespeare
6. Sophocles
7. Virgil

Composers and musicians

1. Johann Sebastian Bach
2. Ludwig van Beethoven
3. Frédéric Chopin
4. Wolfgang Amadeus Mozart

Explorers

1. Hernán Cortés
2. Francis Drake
3. Vasco da Gama
4. Ferdinand Magellan

Inventors and scientists

1. Nicolaus Copernicus
2. Charles Darwin
3. Thomas Edison
4. Albert Einstein
5. Galileo Galilei
6. Carolus Linnaeus
7. Isaac Newton
8. Louis Pasteur
9. Leonardo da Vinci

Mathematicians

1. Archimedes
2. Euclid
3. Leonhard Euler
4. Karl Friedrich Gauss
5. Gottfried Leibniz
6. Pythagoras
7. Ptolemy

Philosophers and social scientists

1. Aristotle
2. Confucius
3. Plato
4. Voltaire

Politicians and leaders

1. Kofi Annan
2. Charlemagne
3. Sitting Bull
4. Timur
5. George Washington
6. Mahatma Gandhi

1. Civilization
2. History of the world
3. Human evolution

Prehistory to Middle Ages

1. Ancient Greece
2. Ancient China
3. Archaeology
4. Bronze Age
5. Iron Age
6. Middle Ages
7. Prehistory
8. Stone Age

Renaissance to Industrial Age

1. Age of Enlightenment
2. European colonization of the Americas
3. History of South Africa in the apartheid era
4. The Holocaust
5. Napoleonic Wars

Industrial Age

1. Scientific Revolution
2. Space exploration

1. City
2. Country
3. Continent

Land types

1. Desert
2. Mountain
3. Ocean
4. River
5. Lake
6. Forest
7. Plains

Continents and regions

1. Africa
2. Asia
3. Middle East
4. North America
5. South America

Countries

1. Argentina
2. Brazil
3. Canada
4. Ethiopia
5. Libya
6. Mexico
7. Nigeria
8. Russia
9. Thailand
10. United States
    1. Gallery of sovereign-state flags

Cities

1. Bangkok
2. Buenos Aires
3. Istanbul
4. Jerusalem
5. Lagos
6. London
7. Mecca
8. Mexico City
9. Moscow
10. New York
11. Rio de Janeiro
12. Rome
13. São Paulo
14. Shanghai
15. Tehran

Bodies of water

1. Amazon River
2. Arctic Ocean
3. Atlantic Ocean
4. Great Barrier Reef
5. Great Lakes
6. Indian Ocean
7. Lake Victoria
8. Mediterranean Sea
9. Niagara Falls
10. Nile
11. North Sea
12. Pacific Ocean

Society

1. Society
2. Family
3. Adult
4. Child
5. Infant
6. Elder
7. Law

Organizations

1. International organizations
2. African Union
3. European Union
4. International Red Cross and Red Crescent Movement
5. Nobel Prize
6. United Nations
   1. World Health Organization
   2. United Nations Children's Fund
   3. United Nations Educational, Scientific, and Cultural Organization
   4. Universal Declaration of Human Rights

Business and economics

1. Agriculture
2. Market
3. Supply and demand

Social issues

1. Sustainable development
2. Freedom
3. Human rights
4. Peace

Culture

Languages and Scripts

1. Alphabet
   1. A, B, C, D, ...
2. Writing system
3. Language
   1. Arabic language
   2. Chinese language
   3. English language
   4. French language
   5. Portuguese language
   6. Spanish language

Literature and Media

1. Writing
2. Book
3. Literature
4. Poetry
   1. One Thousand and One Nights
   2. Mahabharata

Philosophy

1. Philosophy
2. Ethics
3. Knowledge
4. Beauty
5. Scientific method

Religion

1. Specific religions
   1. Buddhism
   2. Christianity
   3. Hinduism
   4. Islam
   5. Judaism

Recreation

1. 1. Chess
   2. Go (board game)
   3. Mancala
   4. Playing cards
2. Sport
   1. Cricket
   2. Football (soccer)

1. Agriculture
2. Food
3. Cheese
4. Fruit
5. Soybean
6. Tobacco
7. Vegetable
8. Oil
9. Chocolate
10. Honey
11. Potato

Spices

1. Salt
2. Sugar

Grains

1. Wheat
2. Bread
3. Rice

Sciences

1. Chemistry
2. Ecology
3. Geology
4. Physics
5. Astronomy
6. Biology

Astronomy

1. Star
2. Planet
3. Solar system
   1. Sun
   2. Venus
   3. Earth
   4. Moon
   5. Mars
   6. Jupiter
   7. Saturn

Physics

1. Solid, Liquid, Gas
2. Energy
3. Heat
4. Gravity
5. Electricity
6. Magnetism
7. Sound

Anatomy

1. Brain
2. Heart
3. Lung
4. Skeleton
5. Stomach
6. Liver
7. Head
8. Eye
9. Mouth
10. Ear
11. Arm

Biology

1. Animal
   1. Bird
   2. Fish
   3. Insect
   4. Human
   5. Dinosaur
2. Bacteria
3. Virus
4. Plant
   1. Grass
   2. Flower
   3. Tree

Medicine

1. Influenza
2. Malaria
3. Treatments
   1. Medication, Penicillin
   2. Vaccine

1. History of technology

Energy

1. Electricity
2. Hydropower
3. Solar power
4. Wind power

Electronics

1. Electronics
2. Battery
3. Incandescent light bulb

Engineering

1. Engine
2. Lever
3. Pulley
4. Wheel
5. Nail
6. Screw
7. Knife

Information technology

1. Calculator
2. Computer
3. Cryptography
4. Writing

Optical

1. Camera
2. Glasses
3. Microscope
4. Telescope

Media and communication

1. Mobile phone
2. Photography
3. Printing

Computers

1. Internet
2. E-mail
3. Operating system
   1. Linux
   2. Microsoft Windows
4. Ethernet
5. Internet service provider

Navigation and timekeeping

1. Clock
2. Compass
3. Pendulum
4. Sundial

Material and chemical

1. Fire
   1. Gasoline
2. Metal
3. Plastic
4. Rubber

Food and health

1. Refrigerator
2. Stove
3. Pasteurization

Space

1. Space exploration
2. Satellite
3. International Space Station

Numbers

1. Digit
2. Integer
3. Natural number
4. Fraction
5. Rational number
6. Pi
7. Prime number

Arithmetic

1. Addition
2. Subtraction
3. Division
4. Multiplication
5. Exponentiation
6. Percentage

Equations

1. Variable
2. Function
3. Infinity
4. Limit
5. Series
6. Algebra

Geometry

1. Line
2. Angle
3. Fractal

Other mathematics

1. Linear algebra
   1. Vector (spatial)
2. Logic
   1. Proof
3. Probability theory
   1. Statistics
4. Trigonometry

1. Metric system
2. Imperial unit
3. Area
4. Volume
5. Scale
6. Mass
7. Thermometer
8. Temperature
9. Speed

Time

1. Clock
2. Calendar
3. Second
4. Day
5. Week
6. Month
7. Season
8. Year

Distance

1. Ruler
2. Metre