category 1

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Across
  1. 3. a shape with four straight lines
  2. 4. a shape with three sides
  3. 5. two side lengths are the same, a kind of triangles
  4. 7. four side lengths are all the same but no right angle
  5. 8. four sides, two of them are parallel but not equal
Down
  1. 1. all side lengths are the same, a kind of triangles
  2. 2. four sides, two of them are parallel and equal
  3. 6. no side lengths is same, a kind of triangle