XVIIInumeral/dɨˈzɔjtu/mediumPortuguesEnglishEspanolFrancaisDefinitionRoman numeral representing the number eighteen (18).The Treaty of Madrid was signed in 1750, in the 18th century.Chapter XVIII of the work is particularly complex.syn18eighteenCommon collocations18th centuryyear 1700EtymologyNumeral romano.Related wordsXVIIXIX18décimo oitavo