syntax

In linguistics, syntax refers to the rules that govern the ways in which words combine to form phrases, clauses, and sentences. More simply, syntax can be defined as the arrangement of words in a sentence. Syntax is one of the major components of grammar.

Paradigmatic and syntagmatic relations

in any grammatical analysis, two types of relationships are possible.

a.    Paradigmatic possibilities are those that can go into the set of alternatives equally in a listed order vertically. For example:

She                  ate               some                               rice                                         

He                              a lot of                                     cake

It                               little                               fruit

The                  big              boy                                  ran                        fast

              Fat              girl                                 sang                      well

              thin             man                                 performed             marvelously

here we see that “she” can be replaced by “he” and “it”, just as “some” can be  substituted by “a lot of” and “little”. So they are said ti be in paradigmatic relations with each other.

Syntagmatic possibilities are those that can go in a sequential pattern, reflecting the restriction on word order horizontally. For example: “she ate some rice” is ordered horizontally, where each word has to follow the other-and it can’t be “she rice some ate” or “ate she some rice”.

Before describing the major and minor classification of words, a look at another dichotomy on word types is necessary.

What is a sentence?
The sentence as a linguistic concept has been defined in over 200 different ways, none of them completely adequate. The grammatical definition of the Sentence is the largest unit to which syntactic rules can apply.  In terms of syntactic categories, most sentences--at least in English-- can be divided into a subject and a predicate.  This applies to sentences with or without a clear topic/comment structure: John ---left. Many sentences have no clear topic and comment structure: It--is raining. (The word it here is the so-called dummy it used to fill the subject slot for impersonal verbs in English; cf. prshí, snezí.) 
Another problem with grammatical, or syntactic, definitions of the sentence is that not all sentences--even in English--are divisible into subject and predicate. Some sentence types make no internal syntactic structure; there is no distinction between subject and predicate:
a) Emotive sentences such as Gee!  Wow. Darn!  Yes!  No! 
b) Imperatives:  Go! Leave! Taxi! All aboard!  Down with alcohol!
c) Elliptic sentences: Who took the car?  John.
d) small talk phrases:  Hello. Good-bye. Good morning.
In polysynthetic languages the single word serve as a complete sentence much more frequently.  In such languages, morphology rather than syntax usually expresses the distinction between subject and predicate.
Types of sentences containing a subject and a predicate
Syntax usually examines sentences that have a clear inner division into subject and predicate.  There are 3 types of subject/predicate structured sentences:
a) a simple sentence contains at least one subject and one predicate:  John read Pushkin.
b) a compound sentence is two or more simple sentences joined into a single sentence:  John read Pushkin and Mary read Updike.  Each simple sentence maintains its own internal syntactic structure.  They may be joined by a coordinating conjunction such as and or or, or asyndetically (without a conjunction).
c) a complex sentence is a sentence in which one of the syntactic roles is played by an embedded sentence:  I made students read Chomsky.  The simple sentence students read Chomsky plays the role of object of the verb made.  Because the syntax of the two parts of a complex sentence is intertwined, it is often not possible to divide them into two free-standing simple sentences.   *I made.  Students read Chomsky.  I saw Mary run. 
Syntactic atoms
The basic unit of syntax is not the word, but the syntactic atom, defined as a structure that fulfills a basic syntactic function. Syntactic atoms may be either a single word or a phrase that fulfills a single syntactic function.
Fido ate the bone.
The dog ate the bone.
The big yellow dog ate the bone.
Our dog that we raised from a puppy ate the bone.
Elements with syntactic equivalence all belong to the same type of syntactic atom (NP, VP)  
A language also contains specific rules for properly connecting syntactic atoms to form sentences--these are called phrase structure rules (look at problem 5 on page 116).  The sentence: The big yellow dog ate the bone. is well formed because it uses the parts of speech in a way that conforms to the rules of English syntax.  The string of words: big the ate bone dog yellow the, is not a sentence because it violates syntactic rules.  It is often not even possible to assign any meaning to a syntactically ill-formed utterance. 
This is why the syntactic rules of a language can be followed perfectly to produce illogical or semantically highly improbable sentences: The bone ate the big yellow dog.  Since a new context could be imagined to render such a statement at least fictionally logical, it is fortunate that our language has a ready made means of expressing it. The fact that syntactic structures are not restricted in the meanings they may express is one reason why we can so easily produce novel sentences never before heard. The semantic independence of the phrase structure rules is one of the main factors that provides for the infinite creativity of human language. Animal systems don't have any structural units that are meaningful yet totally independent of meaning.
Syntactic Relations and phrase structure rules
Let's examine syntactic relations within English sentences.  One approach is to divide the words of a sentence into phrases (defined as words closely associated with one another syntactically).  This technique is know as parsing.  The most fundamental division is between subject and predicate. (of course, this is because we are cheating and ignoring sentence types that lack this division).  Phrases containing different parts of speech can serve one and the same function.
The big yellow dog //ate /bones 
He //ate the old bone.
The big yellow dog //slept.
The dog //growled at John.
Each of these sentences consists of a subject and a predicate.  But in each sentence different syntactic types of words or combinations of words constitute subject and predicate.  Different combinations of parts of speech fulfilling the same syntactic function are said to be syntactically equivalent.  It is possible to write rules describing syntactic equivalence.  These rules are called phrase structure rules. These rules use special symbols designed exclusively for syntactic descriptions.  Grammatical terms or graphic notation devices devised to describe language structure are examples of meta-language, defined roughly as language about language.  The syntactic metalanguage used in writing phrase structure rules involves mainly abbreviations from English words for parts of speech.
S--> NP VP  A sentence consists of a noun phrase and a verb phrase. (These correspond to subject and predicate.)
NP--> (art) (adj) N or NP --> pronoun.