Well, it sort of is, except in the 70s they were talking about the total number of gear combinations, and now it refers just to the rear cassette.

Your 10-speed then had a total of ten total gear combinations available -- probably a double up front and a five-speed in the back. Now the 9 versus 10 speed designation refers only to the rear cassette: so if you have a triple chain ring up front and a 10-speed cassette in the rear, that means you have a total of 30 gear combinations available. If you have a double chain ring in the front and a 9-speed cassette in the rear, you have 18 gear combinations.

But 18-speed and 30-speed sound sort of ridiculous so the terminology has changed. I do see Craigslist ads advertising "27-speed women's bike," though.