Diction and syntax are two major elements of style in communication. Diction refers to the specific choices of words that a speaker or writer uses, while syntax refers to how the words are arranged to form a sentence. A text with complex diction will usually also have complex syntax and vise versa, but the two are actually separate aspects of style. Together, diction and syntax play a large part in the tone, readability, and interest of a text.
A piece of work's diction is made up of the types and variety of words that an author uses. It can be made up of simple, common words, or of unique or technical jargon. For instance, the words "cow" and "bovine" mean the same thing. "Cow" is common diction, however, while "bovine" is more specialized.
Syntax, on the other hand, has to do with the way words are arranged, rather than what particular words are chosen. Like diction, syntax can be either simple or complicated. A sentence with complicated syntax may contain many dependent clauses or unique grammatical features.
A good communicator is aware of the effect that his or her sentence structure and vocabulary choices have on the reader. He or she will use diction and syntax to convey a tone appropriate to the situation. If writing a children's book about cats, for instance, the writer will probably not refer to them as "felidae," and he or she will probably use very simple sentence structures. If writing for a peer-reviewed journal, however, more scientific word choices and complex sentences can be expected.
Readability is an important way in which diction and syntax effect a piece of writing. By adopting verbiage that is polysyllabic or sesquipedalian and by constructing sentences in a manner that may obfuscate the meaning of a text by the proliferation of clauses, an author may reduce his or her readability. In other words, simple sentences and words are easier to read. Sentences with long, uncommon words are harder to read than sentences that use basic vocabulary.
Appropriate and varied diction and syntax also make a text more interesting. Although shorter sentences and simpler vocabulary are easier to understand, re-using the same words over and over can make a piece of writing boring. Constantly using short sentences may make the reader feel like he is or she being "talked down to," and will not hold interest. An author who varies these two elements, within the bounds of what is appropriate for the situation and audience, typically makes the most effective and interesting communicator.