What is a sonnet?

Earlier I wrote an entry on the important poem, the sonnet. But I also know that the sonnet is incredible versatile, almost as versatile as it is important, and further I think it's my task to tell you all a bit more about this almost mythical form of poetry, starting with its history.
But first, I'll list a couple of sources, as you might want to check them out.
The Norton Anthology, English Literature
The Norton Anthology, American Literature
Prof. J. S. Drangsholt of the University of Stavanger.
Prof. B. S. Rangnes of the University of Stavanger.

The sonnet comes from Italy. "Sonnet" is a version of the Italian word "sonnetto", meaning little song.
The father of the sonnet is said to be Francesco Petrarca (1304-1374).
He dealt with love, mostly with the unrequited love.
The Petrarchan (or Italian) sonnet consist of 14 lines (verses).
It's divided by an
Octave consisting of eight lines
Sestet consisting of six lines.
The Octave is mostly closed in its rhyme pattern, showing the abba abba.
The Sestet can vary in its rhyme pattern, for instance cdecde, cdccdc, cdedce etc (this is called inerlaced rhyme)

Now that the sky and the earth and the wind are silent
and the beasts and the birds are stilled by sleep,
night draws the starry chariot in its course
and in its bed the sea sleeps without waves.
I see, I think, I burn, I weep, and she who fills me with sorrow
is always before me in my sweet suffering,
I am in a state of war, full of pain and anger,
and only in thinking of her do I have any peace.

Thus only a clear and living fountain
can still the sweet bitterness on which I feed.
One hand alone can heal and pierce me
therefore my suffering can never be concluded.
A thousand times a day I die, and am reborn
so that I am always far from my salvation.

Ok, this is translated from Italian to English, and the rhyming at the end of each line has been lost in translation. But the original has an abba, abba, cde, cde pattern.
In poems like this they made use of imagery, and also of conflicting imagery. I want you look at the phrase "Sweet Suffering", and think for a second what that conveys. This is a phenomenon we refer to as an oxymoron. In an oxymoron you have two opposite elements placed together in order to explain a certain emotion or state of mind, or even scenery (when describing anything, really). If you're thinking about joining the literally world on a higher level, oxymoron is one of those terms that will come in handy... and if mentioned on an exam, well bring on that A...

Enter Shakespeare.
William Shakespeare (1564-1616)

In a Shakespearean sonnet other rules applies.
We get terminologies such as iambic pentameter, and the rhyming pattern changes drastically. Where the Petrarchan sonnet is divided in two, the Octave and the Sestet, the Shakespearean sonnet is divided in four, three quatrains and a couplet. The rhyming pattern in the quatrains would vary, almost like any stanza of any poem, and then the rhyming couplet would serve as the concluding lines in the end.

Shall I compare thee to a summer's day?
Thou art more lovely and more temperate:
Rough winds do shake the darling buds of May,
And summer's lease hath all too short a date:

Sometimes too hot the eye of heaven shines,
And often is his gold complexion dimm'd;
And every fair from fair sometime declines,
By chance, or nature's changing course, untrimm'd;

But thy eternal summer shall not fade,
Nor lose possession of that fair thou owest;
Nor shall Death brag thou wander'st in his shade,
When in eternal lines to time thou growest;

So long as men can breathe, or eyes can see,
So long lives this, and this gives life to thee.

My favorite are the Shakespearean sonnets. They are more restricted, yes, but showing great poetry through restricted rules is much more challenging in my mind.
But I find it useful to know the different between the two. You might identify many sonnets now that you know, because in the entire literary history of the western world you will find the sonnet in many variations. And I'll give you a few more examples in entries to come, but one more here...
This is so extremely fascinating, I'm sure you all agree, and fascinating simply must be investigated further, so stay with me :-)=

One of the most important poems we went through in our British part of the course last semester was William Wordsworth's Lines (Composed a few miles above Tintern Abbey)
This is really no sonnet at all. It is a dramatic monologue, a technique Wordsworth developed with his good friend Coleridge.
Quickly, a dramatic monologue has a narrator (an "I", a speaker), one narrator. But, he has an audience, he's addressing someone who is present. Had the narrator been alone, speaking into the void it would have been a soliloquy. In Tintern Abbey, Wordsworth is speaking to his sister.
Now Tintern Abbey is a magnificent piece of literature, and so incredibly descriptive of the romantic period. I'm not going to go into the vastness that is Tintern Abbey, I think that will have to be an entry of its own. But I am going to claim something that not even my professor have said out loud... I'm pretty sure she thought it, because she's Oxford material, but out loud this idea is mine.
A few years down the line, you can all say you read it here first...
In Tintern Abbey one can find a climax to the story. My professor pointed us in the general direction. And here is my sentiment. The climax is a hidden sonnet.
...
For I have learned to look on nature, not as in the hour
Of thoughtless youth; but hearing oftentimes
The still, sad music of humanity,
Nor harsh nor grating, though of ample power
To chasten and subdue, And I have felt
A presence that disturbs me with the joy
Of elevated thoguhts: a sense sublime
Of something far more deeply interfused,
Whose dwelling is the light of setting suns,
And the round ocean and the living air,
And the blue sky, and in the mind of man:
A motion and a spirit, that impels
All thinking things, all objects of all thought,
And rolls through all things.
...

Now, if that's not fourteen important lines, I have misunderstood completely about the sonnet.
And from what I've told you, is this a Petrarchan or Shakespearean sonnet?
I should have written my exam on Wordsworth's dramatic monologue, and I'll regret not doing that forever...
I'll be back with more, in the meantime, have a great weekend.