The term 'TYPE OF LOGARITHM' can be answered by two crossword solutions: NATURAL (7 letters) and LOD (3 letters). NATURAL logarithms are logarithms with base e, which is an irrational number approximately equal to 2.71828. They are also known as Napierian logarithms or hyperbolic logarithms. Logarithms of order (LOD) are logarithms with base 10. They are also known as common logarithms or Briggsian logarithms.