Once upon a time, there was no such thing as a martini. This made all the olives very sad.
So the olives unionized and invented cocktail hour and James Bond.
A traditional martini is made with gin and a splash of dry vermouth, and is garnished with the aforementioned olive or a lemon twist.
According to My Friend the Internet, the martini was invented during the 1870s by a bartender named Jerry Thomas (not related to the English Muffins). Except the drink wasn’t anything like today’s martini and it was named Martinez, so in my book it’s a bit questionable. And it included two dashes of maraschino, so ick and highly questionable.
Fast forward to before WWI and an Italian immigrant bartender named Martini di Arma di Taggia at the Knickerbocker Hotel in New York City who invented a drink that is pretty much the modern martini but in different proportions. Or maybe it was named after Martini & Rossi vermouth. Either way, over the years, the drink morphed and voila! we have the modern martini.
A dry martini contains even less vermouth. A “dirty” martini is a martini that’s been slightly diluted with olive juice. If you switch out the olive for a cocktail onion, it’s called a Gibson. And when you make the drink with vodka you can call it a kangaroo (or a vodka martini, but that seems boring).
Do not keep vermouth more than a month after it’s been open. Unlike your parents, it won’t age well.