1. imaginary number (mathematics) a number of the form a+bi where a and b are real numbers and i is the square root of -1
  2. pure imaginary number an imaginary number of the form a+bi where a is 0
  3. imagery the ability to form mental pictures of things or events
  4. ignorant uneducated in general; lacking knowledge or sophistication
  5. imagination image a mental image produced by the imagination
  6. Avogadro number the number of molecules in a mole of a substance
  7. irrational number a real number that cannot be expressed as a rational number
  8. imaginary place a place that exists only in imagination
  9. magic number the atomic number of an extra stable strongly bound atomic nucleus: 2, 8, 20, 28, 50, 82 or 126
  10. imaginary creature a creature of the imagination
  11. ignorance the lack of knowledge or education
  12. imaginary not based on fact; unreal
  13. ordinal number the number designating place in an ordered sequence
  14. imagination the ability to form mental pictures of things or events
  15. imaginary being a creature of the imagination
  16. imaginary part the part of a complex number that has the square root of -1 as a factor
  17. atomic number quantity of protons in the nucleus of an atom of an element
  18. algebraic number root of an algebraic equation with rational coefficients
  19. Avogadro's number the number of molecules in a mole of a substance
  20. Mach number the ratio of the speed of a moving body to the speed of sound