Hellenic: Greek. The name for Greece in Greek is "Hellas."

Lacedaemon or Crete: "Lacedaemon" is another name for Sparta, in ancient times the southern-most major city-state on the Greek mainland. Crete is a large Greek island in the Mediterranean.

Plato: (427?-347? BCE) Greek philosopher and author of The Republic and other works, such as his Socratic dialogues, including this one.

The Prison of Socrates: Socrates (470?-399 BCE) Athenian philosopher and teacher of Plato, was condemned to death for corrupting the youth of Athens by teaching them the principles of his philosophy. This dialogue takes place shortly before the sentence was carried out.

"The third day hence, to Phthia shalt thou go.": Socrates is quoting Homer's Iliad, 9:363, where Achilles talks about abandoning the war against Troy and returning home to Phthia.

the ship from Delos: Delos is a small Greek island in the Aegean Sea. The ship in question was a special one with religious significance, and executions could not take place if it were on a voyage.

Sunium: A Greek island in the Aegean, closer than Delos to Athens.

Thebes, Megara: Thebes was a city in eastern Greece. Megara was a city on the isthmus of Corinth in central Greece.

Thessaly: A region of Greece north of Athens on the Aegean.