As far as I’m concerned, to make a martini correctly, you must make it with both gin and (dry) vermouth. Some people maintain that a martini is better without vermouth. I don’t consider gin shaken (or stirred) with ice, strained into a cocktail glass, and garnished with olives to be a martini. It’s cold gin. The vermouth is an essential ingredient, as gin by itself is quite vile.
Some people substitute vodka for gin, calling it a vodka martini. Since the vermouth only accounts for about a quarter of the drink, I don’t see how this qualifies as any kind of martini.
Then there are the numerous other martinis, such as the black martini and the lemon drop martini, which generally contain neither gin nor vermouth, and aren’t even garnished with olives either. The only claim to the name of martini that these drinks have is that they are served in a cocktail glass (which the people that drink them probably call a martini glass). A far better term for these drinks would be “cocktail”.
The rest is a matter of taste, as far as I’m concerned. Whether the drink is shaken or stirred has only a minor effect on the finished product. The amount of vermouth to use is also a matter of taste. I happen to like them about four to one, but as long as there’s a few drops in there, it can still be a martini.
But, true to the nature of this forum, this is all just my humble opinion.
A real martini is gin, vermouth, a piece of lemon peel twisted above the glass-gives it that oily consistency, and an olive. Anything else is just a cocktail.
The amount of vermouth is pretty arbitrary-I’ve seen recipes that were almost, but not quite, gin. However, if it doesn’t have vermouth in it, it’s just gin, not a martini.
A martini, as defined by both Webster’s and Randon House, is made with gin or vodka and
vermouth. A gin martini, at least in the classier places, is often called a classic martini, but a good
bartender won’t curl his lip when asked for a vodka martini. Those other fru-fru drinks they
call martinis these days are some other matter.
I prefer not to have either my vodka or gin diluted with water, so I don’t use ice. Vodka I keep
in the freezer anyway, and when I make a gin martini, I chill the gin in a pitcher that has an
ice inset (although I will admit to using those fake icecubes, but I was in the wilderness of a
friend’s house–with a woefully inadequately stocked bar). The amount of vermouth is subjective,
thus the common request for a "dry’ martini. I pour a tad of vermouth into a chilled glass, roll it to cover
the insides, flick the remaining liqud out, and then quickly pour in the gin or vodka. When I make
a pitcher, I put little vermouth in, because it can be added to an individual’s glass if the want it
‘wetter’. And I stir, not shake, see comment above about the ice. I do love martini shakers,
but i use them for other drinks.