Definition
Syntax is the grammatical arrangement of words in a sentence.
It concerns both word order and agreement in the relationship between words.
Syntax is primarily concerned with structure of sentences.
Examples
The following statements follow normal English word order:


The cat sat on the mat.
My old brown leather suitcase.
The following statements do not follow normal English word order:


The cat on the mat sat.
My brown leather old suitcase.
Use
Word order is very important in English, because the language is no longer inflected.
That is, individual words do not have endings to show which parts of speech they
represent.
Changes to conventional synatx are often used to create dramatic, poetic, or comic
effect.
For instance, poets and song lyricists often change syntactic order to create rhythmic
effects:
"I'll sing to him, each spring to him
And long for the day when I'll cling to him,
Bewitched, bothered and bewildered am I."
[COLE PORTER]
A normal sentence in English usually contains at least three elements: subject, verb,
and object.
Subject
The cat
John
Mary
Verb
eats
likes
chose
Object
the goldfish
football
the wallpaper
Every language has rules of syntax, and to the linguist the essential rules are
descriptive. They are the rules which underpin the life of the language and which are
extremely slow to change.
These are not to be confused with the presecriptive 'rules' of traditional grammar [For
instance, 'Never end a sentence with a preposition'].
An example of a descriptive rule of English syntax is that in the imperative in English,
the verb takes the initial position in the sentence, usually directly before the noun which
is the object.




Put those books on the table.
Take the lid off after half an hour.
Remove all packaging before heating the soup.
Isolate the switch in case of fault.
It is important to make a distinction between grammar and syntax, and to realise that
syntax is a component of grammar.
The term 'grammar' refers to the whole structure of the language including the naming
of its parts, its rules of tense, and its sound system. It is a comprehensive term.
Syntax only refers to the relationship between the grammatical components of language
in use. In other words it is the nature, quality or type of relationship between terms in any
given statement which is the province of syntax.
The construction of the passive voice is a syntactic issue, as it involves word order. The
following statement is in the passive voice:

A woman was run over in central London today by a vehicle travelling at high
speed.
If we transfer this to the active voice, we have:

A vehicle travelling at high speed ran over a woman in central London today.
The semantic content is similar in the two statements, but the emphasis is changed
according to whether it is expressed as active or passive.
The difference between the two versions is dependent on the positioning of the subject
and the object in the sentence. In the passive version, the object takes the initial position.
This is a syntactic principle.
http://www.buzzin.net/english/syntax.htm