18 (number)  18 (eighteen) is the natural number following 17 and preceding 19. In most countries, 18 is the age of majority (adulthood) and also the voting age. In eleven states of the United States, 18 is the age of sexual consent. In most US states and pursuant to federal law, 18 is the minimum age to purchase firearms (with the exception of handguns) 18 is also the minimum age to get married without parental consent. It is also the age of sexual consent under U.S. federal law (although this law only applies in circumstances involving transportation or transaction between different states or outside the United States). In addition, Pennsylvania has a corruption of minors law that makes the "de facto" age of consent there 18. This is also the case in some jurisdictions outside the United States, including Canada. Eighteen is also: