Basic Sentence Structure

The most common sentence formation in English is the following:
Subject  +  Verb  +  Object  +  Complement

Note: Subjects and Verbs are always necessary. Objects and Complements are used or not, depending on the idea you need to express.

I dream = Subject + Verb
He found it = Subject + Verb + Object
They arrived in the evening. = Subject + Verb + Complement
She called us last night. = Subject + Verb + Object + Complement

Subjects
The subject of a sentence or clause is the part of the sentence or clause about which something is being said. It is usually the doer of the action.

A subject can be:

• Noun: Java is a programming language.

• Pronoun: It is an object-oriented language.

• Phrase: This language was developed in the early 90s.

• Clause: How similar it is to C# has been mentioned in several texts. 

A noun is a single word that represents a person, animal, thing, place, feeling, etc. 
A pronoun is a word that substitutes a noun. 
A phrase is a group of words that lacks subject, verb, or both.
A clause is a group of words that contains one subject and one verb. 

Verbs
Verbs express action or state of the subjects. There are three types of verbs:

• Transitive: Mark downloaded a new antivirus. 

• Intransitive: He works at Sun Microsystems.

• Linking: He is a technical support agent. 

A transitive verb has a direct object.
An intransitive verb does not have a direct object.
A linking verb gives additional information on the subject. 

Objects
Objects receive the action of the verb. They can be either direct or indirect.

• Direct Object: Windows replaced DOS in most computers. 

• Indirect Object: Paul recommended Lisa a new application. 

Direct Object receives the action of the verb directly.
The indirect object cannot exist without a direct object. When both objects are present, the direct object answers the question "what?" and the indirect object answers the question "whom?"

Complements
Complements answer questions like:

• When: ASP.NET was developed in 2002.
• Where: They developed that application at Ekosoft.
• Why: Java is similar to C# because Java is based on C#.
• How: It scans your system very fast. 
• How often: That application usually fails. 
• What for: They installed a new accounting system to prevent issues. 

After a linking verb, there is a copulative complement.

• Java is a programming language