My crossword puzzle

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Across
  1. 3. The size of a surface
  2. 5. Not consistent or having a fixed pattern; liable to change
  3. 7. The branch of mathematics concerned with the properties and relations of points, lines, surfaces, solids, and higher dimensional analogs
  4. 8. The sixteenth letter of the Greek alphabet (Π, π), transliterated as ‘p.’
  5. 9. A surface of which one end or side is at a higher level than another
Down
  1. 1. The part of mathematics in which letters and other symbols are used to represent numbers and quantities in formulae and equations
  2. 2. The branch of mechanics concerned with bodies at rest and forces
  3. 4. 1.The space between two intersecting lines or surfaces at or close to the point where they meet
  4. 6. 1.A statement that the values of two mathematical expressions are equal (indicated by the sign =)