Every sentence follows a pattern. This is what makes it grammatically correct.

Before we can understand sentence patterns, we need to know what the different parts of a sentence are.
1. Subject (S): The subject is sometimes called the naming part of a sentence. The subject shows what the sentence is about or who or what performs the action.
Ramu built a house.
In this sentence, 'Ramu' is the Subject (S).
2. Verb (V): Verbs are the action words in a sentence. Verbs describe what the subject is doing. Verbs include words like 'love', 'agree', 'feel', 'am' and 'have'.
Ramu built a house.
In this sentence, 'built' is the Verb (V).
3. Direct Object (DO): The Direct Object in a sentence is the entity that is acted upon by the subject
Ramu built a house.
In this sentence, 'a house' is the Direct Object (DO). 
4. Indirect Object (IO): The Indirect Object gives information about to whom/what or for whom/what the action was made. The Indirect Object only follows the Direct Object.
Ramu built a house for Janu.
Here, 'Janu' is the Indirect Object (IO).  
5. Complement (C): It's a word, clause, or phrase that's needed to complete a given expression.
Every child is a gift.
In this sentence, 'gift' is the Complement (C).
6. Adverbial / Adjunct (A): The adverbial/adjunct is an optional part of a sentence. That means it will not affect the remainder of the sentence if it is not mentioned.
Thomas helped Sampath in the Nehru stadium.
In this sentence, 'in the Nehru stadium' is the Adverbial/Adjunct (A).
In grammar, a sentence is the basic grammatical unit. It contains a group of words and expresses a complete thought. A sentence consists of a subject and a predicate. For example, in the sentence "Tagore writes good poems" Tagore is the subject of the sentence and writes good poems is the predicate.
There are six basic or simple sentence patterns:
  1. Subject/Predicate, Action Verb
  2. Subject/Predicate, Action Verb/Direct Object
  3. Subject/Predicate, Action Verb/Adverb
  4. Subject/Predicate, Linking Verb/Predicate Nominative
  5. Subject/Predicate, Linking Verb/Predicate Adjective
  6. Subject/Predicate, Action Verb/Indirect Object/Direct Object
Sentences from the lesson "The Great Stone Face II":
Sentence Patterns
Parts of the Sentence Pattern
Ernest speaksS (Subject): Ernest
V (Verb): speaks
S+V+ A
Ernest preaches beautifully S (Subject): Ernest
V (Verb): preaches
A (Adverbial): beautifully
Ernest preaches his neighbours every eveningS (Subject): Ernest
V (Verb): preaches
DO (Direct Object): his neighbours
A (Adverbial): every evening
Usually the poet is very imaginative A (Adverbial): Usually
S (Subject): the poet
V (Verb): speaks
C (Complement): very eloquently
Every evening Ernest stared at The Great Stone Face mountain for long hours
A (Adverbial): Every evening
S (Subject): Ernest
V (Verb): stared
IO (Indirect Object): at The Great Stone Face mountain
DO (Direct Object): for long hours
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