Which ingredient can change a dry martini into wet martini?

Here's why:

* Dry Martini: A dry martini is characterized by a very small amount of vermouth, usually just a dash or a spray. This results in a strong, gin-forward flavor.

* Wet Martini: A wet martini uses a larger amount of vermouth, making the drink more flavorful and less gin-forward.

Essentially, the difference lies in the ratio of gin to vermouth.