A sonnet, derived from the Italian word ‘sonetta’ meaning little song, is 14 lines of iambic pentameters of complicated rhyming structure and finishing in a rhyming couplet. Shakespeare used the sonnet to document and immortalize (some say) his own life, and wrote 154 of them – each one usually being a sequel to the one that precedes it.
Their structure always remains the same with three four-line stanzas, or quatrains, and ending with the two-line rhyming unit called a couplet. The rhyming lines in the three stanzas being, always, the first and third lines and the second and fourth lines.
Many of the sonnets are like little plays or soliloquies, in that the author/poet/speaker is in a dramatic situation, and therefore needing to talk or communicate - there being some kind of development from beginning to end and an intent to convey it.
Time and time again words are used with double-meanings, or used ironically, with the purpose of inducing measured response in its impart.
The best known, and probably the most favoured sonnet, is almost certainly Sonnet 18, although, for me, it is without doubt Sonnet 138 and which provides for a superb example of the structure!
When my love swears that she is made of truth,
I do believe her though I know she lies,
That she might think me some untutor'd youth,
Unlearned in the world's false subtleties.
Thus vainly thinking that she thinks me young,
Although she knows my days are past the best,
Simply I credit her false-speaking tongue:
On both sides thus is simple truth suppressed:
But wherefore says she not she is unjust?
And wherefore say not I that I am old?
O! love's best habit is in seeming trust,
And age in love, loves not to have years told:
Therefore I lie with her, and she with me,
And in our faults by lies we flatter'd be.