Subject, Verb, Complement & Modifier

Subject

The subject is the agent of the sentence in the active voice, subject is the person or thing that does the action of the sentence and subject normally precedes the verb.
Note: Every sentece in English must have a Subject
Example : Coffee is delicious
Milk contains calcium
The subject may be a noun phrase. A noun phrase is a group of words ending with a noun. (it can't begin with a preposition).
Example : The book is on the table
That new red car is John's
In some sentence there is not true subject. However it and there can often act as pseudo-subjects and should be considered as subjects.
Example : It is a nice day today
There was a fire in that bilding last month

Verb

The verb follows the subject, it generally shows the action of the sentence.
Note : Every sentence must have a verb
Example : John drives too fast
They hate spinach
The verb maybe a verb phrase. A verb phrase consists of one or more auxiliaries and one main verb. The auxiliaries always precede the main verb.
Example : John is going to Miami tomorrow
(auxiliary is; main verb going)
Jane has been reading that book
(auxiliary has, been; main verb reading)

Complement

A complement completes the verb. It is similar to the subject because it's usually a noun or noun phrase, However, it generally follows the verb when the sentence in the active voice.
Note : Every sentence doesn't require a complement
The complement can't begin with a preposition
Example : He was smoking a cigarette
John bought a cake yesterday

Modifier

tells the time, place or manner of the action. Very often it's a prepositional phrase. Prepotional phrase is a group of words that begins with a preposition and ends with a noun.
Note : A modifier of time usually comes last if more than one modifier is present.
Example of prepositional phrases :
In the morning, at university, on the table
A modifier can also be an adverb or an adverbial phrase :
Last night, hurriedly, next year, outdoors, yesterday
Example : John bought a book at the bookstore
(modifier place)
Jill was swimming in the pool yesterday
(modifier of place)(modifier of time)
Note :
The modifier normally follows the complement, but not always. However, the modifier, especially when it's a prepositional phrase, usually can't separate the verb and the complement.
Example : She drove the car on the street
(verb) (complement)

Exercise
Identify the subject, verb, complement, and modifier in each of the following sentence.

1. George is cooking dinner tonight
2. Henry and Marcia have visited the president
3. We eat lunch in this restaurant today
4. Pat should have bought gasoline yesterday
5. Trees grows
6. It was raining at seven o'clock this morning
7. She opened her book
8. Harry is washing dishes right now
9. She buy pineaple in the market
10. They were watching tv a few minutes ago

*Answer*
1. George/ is cooking/ dinner /tonight
(subject) (verb phrase) (complement) (modifier of time)
2. Henry and Marcia/ have visited/ the president
(subject) (verb phrase) (complement)
3. We /eat/ lunch /in this restaurant /today
(subject) (verb phrase) (complement) (modifier of place)(modifier of time)
4. Pat /should have bought /gasoline /yesterday
(subject) (verb phrase) (complement) (modifier of time)
5. Trees /grows
(subject) (verb phrase)
6. It/ was raining /at seven o'clock this morning
(subject) (verb phrase) (modifier of time)
7. She /opened /her book
(subject) (verb phrase) (complement)
8. Harry /is washing /dishes /right now
(subject) (verb phrase) (complement) (modifier of time)
9. She /buy /pineaple /in the market
(subject) (verb phrase) (complement) (modifier of place)
10. They /were watching /tv /a few minutes ago
(subject) (verb phrase) (complement) (modifier of time)