18 days until "Fun on a Boat!!!!!!"
The atomic number of argon.
The 18-electron rule is a rule of thumb in transition metal chemistry for characterising and predicting the stability of metal complexes.


The Hebrew word for "alive" is חי (chai), which has a numerical value of 18. Consequently, the custom has arisen in Jewish circles to give donations and monetary gifts in multiples of 18 as an expression of blessing for long life.
In Chinese tradition, the number 18 is normally 十八 (shí bā), but it can also be read as 幺八 (yāo bā), which sounds like 要发 (yào fā), meaning that one is going to prosper. Thus, building floors numbered "18" are often very expensive in China.Contrastingly, though, the floor 18 of a building in Northern China is viewed as a floor to be avoided, as one can never return from the 18th level of hell.
In many countries 18 is the age of majority (legal adulthood).
The number of holes in a stipulated round of golf.
The number of wheels on the most common type of North American tractor-trailer truck, which are hence often called 18-wheelers.