The Lyceum (Greek: Λύκειον, Lykeion) was Aristotle's philosophical school, named after its site at an Athenian public exercise park, or "gymnasium". The name derived from the dedication of the gymnasium to Apollo Lyceus.
Aristotle founded the school upon his return to Athens in c. 334 BCE after a period spent in Macedon as the tutor of the young prince Alexander (who later became known as Alexander the Great). Aristotle and the students of the Lyceum became known as the "peripatetics", because of their habit of walking up and down while discussing philosophy (an alternative, though related, derivation is from the peripatos, or covered stoa in the Lyceum garden where Aristotle lectured).
Aristotle taught and developed his philosophical theories in the Lyceum for eleven years, until the death of Alexander in 322 BCE led to the public release of anti-Macedonian feelings; Aristotle was charged with impiety (the same charge which had led to the execution of Socrates), and was forced to leave for exile in Macedon. He died a year later.
The Lyceum survived the death of Aristotle, however. Theophrastus (d. ca. 287), took over the leadership of the school and continued Aristotle's research. Theophrastus is particularly remembered for his book The Characters, a discussion of different character types, and for his research on plants. Strato of Lampsacus (d. ca. 269) continued the Lyceum after the death of Theophrastus, but it probably ceased to be an active school with the death of Strato.
Though the Lyceum was no longer an active school, the tradition of Greek philosophical schools working on Aristotle continued at least until Justinian closed the Academy in Athens in 529 CE. Though much of this intellectual activity is categorized under the heading of Neoplatonism, Aristotle's influence remained central to the Neoplatonic project. In fact, one of the central projects of Neoplatonism (and of Proclus in particular) was the pursuit of what Robert Wisnovsky calls the "Greater Harmony"-- the synthesis and reconciliation of Aristotle and Plato.
- Cambridge Companion to Arabic Philosophy, p. 97.