1. substitute a person or thing that can take the place of another
  2. substantive having a firm basis in reality and therefore important
  3. substitutable capable of being exchanged for another or for something else that is equivalent
  4. substitutability exchangeability by virtue of being replaceable
  5. substituting working as a substitute for someone who is ill or on leave of absence
  6. subsequent following in time or order
  7. obstinate marked by tenacious unwillingness to yield
  8. substitution putting one thing or person in the place of another
  9. substantive dye dye with a high affinity for cellulose fibers
  10. substandard falling short of some prescribed norm
  11. substantival of or relating to or having the nature or function of a substantive (i.e. a noun or noun equivalent)
  12. substructure the basic structure or features of a system or organization
  13. substrate the material that is acted upon by an enzyme
  14. subsidiary functioning in a supporting capacity
  15. substitution class the class of all items that can be substituted into the same position (or slot) in a grammatical sentence (are in paradigmatic relation with one another)
  16. constitutive essential in the structure of something
  17. destitute poor enough to need help from others
  18. subsistence a means of surviving
  19. statutory relating to or created by regulations
  20. subsister one who lives through affliction