Merriam-Webster Collegiate Dictionary - substantive

 I. noun  Etymology: Middle English substantif, from Anglo-French sustentif, from sustentif, adjective, having or expressing substance, from Late Latin substantivus, from Latin substantia  Date: 14th century noun; broadly a word or word group functioning syntactically as a noun  • substantivize transitive verb  II. adjective  Etymology: Middle English, from Anglo-French sustentif  Date: 14th century  1. being a totally independent entity  2.  a. real rather than apparent ; firm need ~ evidence to prove her guilt; also permanent, enduring  b. belonging to the substance of a thing ; essential  c. expressing existence the ~ verb is the verb to be  d. requiring or involving no mordant a ~ dyeing process  3.  a. having the nature or function of a grammatical ~ a ~ phrase  b. relating to or having the character of a noun or pronominal term in logic  4. considerable in amount or numbers ; substantial made ~ progress  5. creating and defining rights and duties ~ law — compare procedural  6. having substance ; involving matters of major or practical importance to all concerned ~ discussions among world leaders  • ~ly adverb  • ~ness noun