Ovid was a Roman poet known for his mythological tales and love poetry.  His works, such as Metamorphoses and Heroides, provided Shakespeare with a rich source of mythological stories, themes, and symbols.  Shakespeare's plays frequently drew on Ovidian myths, incorporating them into the narrative and exploring themes of transformation, desire, and the complexities of love.

Seneca was a Roman philosopher, playwright, and tragedian.  His works, particularly his tragedies, had a significant influence on Shakespeare's exploration of tragedy as a genre.  Shakespeare's tragedies, such as Hamlet, Macbeth and King Lear, show the influence of Seneca in terms of their themes of fate, revenge, and the internal conflicts of the tragic heroes.

Plutarch was a Greek historian and biographer whose Lives of the Noble Greeks and Romans provided Shakespeare with historical material for his Roman plays.  Shakespeare drew extensively from Plutarch's accounts of Julius Caesar, Mark Antony, and other historical figures, using them as a basis for his own interpretations of their characters and actions.

Petrarch was an Italian poet and scholar known for his sonnets and his idealized love for "Laura."  His poetry popularized the Petrarchan sonnet form, which Shakespeare utilized in his own sonnets.  The themes of unrequited love, idealized beauty, and the complexities of human emotion found in Petrarch's works influenced Shakespeare's exploration of love and desire.

Boccaccio was an Italian writer and poet known for his collection of stories called The Decameron.  His tales encompassed various themes and genres, including romance, tragedy, and comedy.  Boccaccio's storytelling style and the range of narratives he presented may have influenced Shakespeare's own narrative structure and the interweaving of multiple plotlines in his playes.

Tragedy as a genre greatly influenced Shakespeare's works.  He drew on classical models of tragedy, such as those of Greek playwrights like Sophocles and Euripides, as well as the Roman tragedians, particularly Seneca.  Shakespeare's tragedies explore themes of human suffering, the fall of great individuals, the consequences of ambition, and the complexities of moral choices.

Mythology, particularly the Greco- Roman myths, provided Shakespeare with a rich source of stories, symbols, and archetypal characters.  He incorporated mythological elements and characters into his plays, using them to explore universal themes, portray human nature, and create dramatic resonance.

Medieval romances, with their tales of chivalry, love, and adventure, influenced Shakespeare's early plays, such as Romeo and Juliet and A Midsummer Night's Dream.  These romances provided inspiration for the portrayal of idealized love, fantastical elements, and the use of mistaken identites and magical transformations.

Morality plays were popular in medieval England and often presented moral lessons through allegorical characters and dramatic scenarios.  While Shakespeare's works are not strictly morality plays, they share some moralistic elements and explore themes of virtue, vice, and the consequences of one's actions.