Syntax refers to the rules of a language and its grammar in terms of ordering words in a sentence so that their meaning is clear.  It is also a way of describing the conventions of how words are arranged and combined so as to create a particular meaning (Beck et al., 2005).

Example:

For English speakers, the first sentence is comprehensible as we are able to derive meaning from the words structured in this order.  The second sentence, though, lacks sensibility because it does not follow the rules of syntax.  The words are placed in a random order, so there is no knowledge of which words are nouns, verbs, adjectives, etc.  This sentence has no meaning and therefore does not follow the conventions of syntax.