[proh-lawg, -log] 
noun, verb, -logued, -logu⋅ing.| 1. | a preliminary discourse; a preface or introductory part of a discourse, poem, or novel. |
| 2. | an introductory speech, often in verse, calling attention to the theme of a play. |
| 3. | the actor or actress who delivers this. |
| 4. | an introductory scene, preceding the first act of a play, opera, etc. |
| 5. | any introductory proceeding, event, etc.: Appetizing delicacies were the prologue to a long dinner. |
| 6. | to introduce with or as if with a prologue. |
| pro·logue also pro·log (prō'lôg', -lŏg') n.
[Middle English prolog, from Old French prologue, from Latin prologus, from Greek prologos : pro-, before; see pro-2 + logos, speech; see leg- in Indo-European roots.] |
prologue
prefatory and supplementary pieces to a literary work, especially a verse drama. The ancient Greek prologos was of wider significance than the modern prologue, effectually taking the place of an explanatory first act. A character, often a deity, appeared on the empty stage to explain events prior to the action of the drama, which consisted mainly of a catastrophe. On the Latin stage, the prologue was generally more elaborately written, as in the case of Plautus' Rudens, which contains some of his finest poetry.
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lɔg