What's the difference between lustration and lustrum?

Lustration

Definition:

(n.) The act of lustrating or purifying.
(n.) A sacrifice, or ceremony, by which cities, fields, armies, or people, defiled by crimes, pestilence, or other cause of uncleanness, were purified.

Example Sentences:

(1) From the 1970s onward, many different forms of accountability were developed, from Latin America to South Africa and from south-east Asia to south-east Europe: truth commissions, judicial investigations, the opening of archives, banning compromised people from holding public office ("lustration"), domestic and international trials.
(2) Yehor Sobelev, a journalist and Maidan activist who now leads the Lustration Committee – a body that wants to force all Ukrainian public officials to undergo checks for past links to corruption and misgovernance – says Poroshenko has not done nearly enough during his time in charge.

Definition:

(n.) A lustration or purification, especially the purification of the whole Roman people, which was made by the censors once in five years. Hence: A period of five years.

Example Sentences:

(1) Thus Imperium (2006) describes the rise to power, Lustrum (2009) the years in power and Dictator (2015) the repercussions of power.