The best replacement for porosity is permeability.

The best alternatives to porosity are rated as following:
★★★★★  permeability
★★  void ratio
★  grain size
★  particle size
★  water saturation
★  effective porosity
★  low porosity
★  secondary porosity
★  hydraulic conductivity
  total porosity
  specific yield
  log porosity
  void fraction
  pore size
  soil permeability
  compressive strength

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Speaking about porosity, one probably shouldn't forget about soil.

Other search terms related to porosity and their ratings are:
★★★★★ soil
loss of bone density
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Google Trends

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porosity
permeability
void ratio