Socrates
Socrates (469-399 BCE) - in Greek Σωκράτης; English pronunciation SOCK-ra-teez, IPA: / 'sɒkrə,tiːz/ - was an Athenian citizen who spent his entire life in Athens. Perhaps prompted by the pronouncement of the Delphic oracle that no one was wiser than he, Socrates devoted much of the later part of his life to cross-questioning those he happened to meet and probing their beliefs about the way we should live. Although he hoped by this means to discover someone wiser than himself and prove the oracle mistaken, his hopes were disappointed. In Plato's early dialogues, which probably reflect the nature of Socratic practice, Socrates' technique of cross-examination always succeeds in showing that his partner in the discussion holds contradictory beliefs and so cannot know what he initially - and sometimes very confidently - claimed to know.
Socrates himself wrote nothing, and we cannot be certain whether, as well as probing the views of others, he also sought to defend a position of his own. Aristotle says (e.g., in Metaphysics A 6, 987b1-4) that Socrates was the first philosopher to appreciate the importance of definitions; and on the evidence of Plato's early dialogues he seems to have been committed to a set of philosophical claims about the nature of morality and its close connection with the happiness or well-being (eudaimonia, εὐδαιμονία) of the individual moral agent - a commitment which would serve to explain his acceptance of the so-called Socratic paradoxes, i.e., the paradoxical statements that have traditionally been ascribed to Socrates, such as the statement that no one voluntarily does wrong.
Socrates was a person of great physical and moral courage, and on a number of occasions had refused on moral grounds to comply with the demands of the authorities in Athens. This principled resistance had made him many enemies, and in 399 he was put on trial for 'introducing strange gods and corrupting the young'. Found guilty and sentenced to death, he refused to escape from prison, as he easily could have done, and died by drinking the hemlock. Plato's (no doubt idealised) account of these events is to be found in three of his dialogues: the Apology purports to be Socrates' defence at his trial; in the Crito Socrates explains why it would be wrong for him to try and escape from prison; and the Phaedo describes the last day of Socrates' life and his death in prison.
See further Socratic irony, Plato, Platonic dialogues, Aristotle
For some help with the pronunciation of Greek names see Pronunciation of Greek Proper Names.