Definition

1. Noun:
   • A ceremonial purification of the Roman population every five years following the census: In ancient Rome, a "lustrum" was a religious rite of purification for the entire populace, performed by the censors at the conclusion of the five-yearly census.
   • A period of five years: By extension, "lustrum" refers to any five-year period, serving as a synonym for a quinquennium.

Usage Examples

• Noun (Ceremonial Purification): The completion of the census was marked by a solemn lustrum. The censor performed the rites of the lustrum to purify the city.

• Noun (Five-Year Period): The project's first lustrum saw significant progress. A full lustrum has passed since the treaty was signed.

Advanced Usage

• The term is primarily used in historical, academic, or literary contexts. In modern usage for a five-year period, "quinquennium" is more common in formal writing, while "five-year period" is standard.
• "To pass a lustrum": to complete a five-year span.

Variants and Related Words

• Lustral (adj): Pertaining to or used in purification; or, occurring every five years.
• Lustration (n): The act, process, or ceremony of purifying.

Synonyms

• Quinquennium: A period of five years.
• Pentad: A group or set of five.
• Five-year period: The standard modern phrasing.

Notes on Meaning

• The two meanings are historically connected. The ceremonial purification defined the conclusion of each five-year census cycle, leading the word to denote the time period itself.
• The plural forms are "lustrums" or, more traditionally, "lustra".

Noun

1. a ceremonial purification of the Roman population every five years following the census
2. a period of five years