Hesychius of Alexandria likely lived and worked during the 5th century CE, though exact dates are uncertain. His famous work, the Lexicon — a massive Greek glossary — suggests he was active sometime between late 4th and early 6th century CE, most commonly estimated around c. 400–500 CE.

Key points:

• Name: Hesychius of Alexandria (Ἡσύχιος ὁ Ἀλεξανδρεύς)
• Work: Lexicon — a dictionary of rare and obscure Greek words, often preserving older, regional, or archaic meanings
• Purpose: Possibly compiled to aid understanding of classical texts, including Homer, tragedians, and early philosophers

The Lexicon is especially valued today because it preserves thousands of words and meanings from earlier Greek dialects, including those no longer attested elsewhere.

It's valued above LSJ (created in victorian era), because Hesychius Lexicon is written (~500CE)
during / right-after the times we're studying as classical philologists.