A function is the job a word is performing in the sentence. video The three basic functions are substantival, adjectival, and adverbial.
A substantive is any word performing a noun function. The basic noun functions are:
Adjectival means that word, phrase, or clause is modifying some noun (or pronoun). Adjectival elements in a sentence tend to answer the following questions: how many? which one? what kind?
Six dogs chased Jeb. (how many dogs?)
The oak tree near the house must be removed. (what kind of tree?)
The large book must be burned. (which book?)
Adverbial means that word, phrase, or clause is modifying some verb. Adverbial elements in a sentence tend to answer the following questions: how? when? where? why?
Jeb ran quickly. (Jeb ran how?)
Jeb studied to earn his degree. (Why did Jeb study?)
Jeb slept under the bridge. (Jeb slept where?)
Jeb ate his food after sunset. (Jeb ate when?)