• A gerund always functions as a noun: either a subject, a direct object, subject complement, or object of preposition.
  
• A gerund always ends in “ing.”
• Gerunds can be modified by adjectives and, because they have some qualities of a verb, can take objects.

In the sentence

Giving money and time to those who are less fortunate marks a person as generous and compassionate.

giving is a gerund, that, as part of a phrase, constitutes the subject of the sentence (marks is the verb). It takes a compound direct object (money and time) and an adverbial prepositional phrase with an embedded subordinate clause (to those who are less fortunate).

• In the first two sentences to the right, the subject is highlighted. Notice how the use of the gerund is identical to the use of a more typical noun.

• A gerund sometimes begins a phrase that, taken as a whole, functions as the subject of the sentence, as in the third and fourth sentences to the right.

1.  Learning begins in infancy.
     (learning, the subject of the sentence, is
     sometimes mistaken by students as a verb.)

2.  Good study habits begin in infancy.
     (habits is easily recognized by all students as a
     noun)

3.  Decorating our house has been a family
     tradition at Christmas for generations.
     (To help students recognize the gerund phrase as
     the subject, ask them, "What has been a family
     tradition?")

4.  Running to the 7-11 for Krispy Kremes,
     however quickly, does not constitute good
     exercise.

• Every clause has two basic parts: the subject, the "actor" of the sentence or clause and the predicate, which expresses the action. 
• Sometimes the predicate consists solely of the verb, as in the first sentence to the right.
• In most cases the predicate consists of the verb and all the words that receive the action or complete the meaning of the sentence, as in the second example to the right.
• When nouns complete the meaning, they can be
  verb complements (direct and
   indirect objects)
  subject complements (a noun
   following a linking verb that defines
   the subject in some way)
  object complements (which follows and
   refers to the direct object)
  
  (see examples to the right of typical nouns performing these functions)

Sentence with simple verb predicate.
Sentence with verb, indirect object, direct object, and prep. phrase.

Verb Complement:
The reformed vampire eyed my neck and gave me a longing look.
(Neck, me and look are all verb complements; neck and look are direct objects, and me is an indirect object. )

Subject Complement:
Only kryptonite was a match for Superman.
(Match is a predicate nominative.)

Object Complement:
The nation elected George Bush president for a second term.
(President is an object complement, referring to George Bush.)

(Note: Try as I might, I could not create a sentence where the gerund functioned as an object complement, so you will not see an example of that function below.)

• In the first sentence to the right, the gerund is being used as a direct object, comparable to the object in the second sentence.
   

• As with subjects, gerund phrases can, as a whole, function as a complement, as in the example to the right.

2.  Before her big date, Eunice considered a hot bath.

3.  After her date, however, Eunice considered donating her evening gown to a charity.
(the gerund donating takes its own direct object,  gown, and the whole phrase functions as the direct object of the verb considered [answering the question "What did Eunice consider?"])

• In the sentence to the right, the gerund is being used as a subject complement.
• A gerund phrase can function as a complement.

The last activity before I retire is brushing my teeth.
(brushing my teeth completes the subject activity)