Ristretto

Ristretto , known in full in Italian as caffè ristretto, is a "short shot" (20 ml (0.7 imp fl oz; 0.7 US fl oz) from a double basket) of a highly concentrated espresso coffee. It is made with the same amount of ground coffee, but extracted (also in from 20 to 30 seconds) using half as much water. A normal short shot might look like a ristretto, but in reality, would only be a weaker, more diluted, shot. The opposite of a ristretto (Italian for 'shortened, narrow') is a lungo ('long'), which has double the amount of water. In France a ristretto is called café serré. Regardless of whether one uses a hand pressed machine or an automatic, a regular double shot is generally considered to be around 14–18 g (0.49–0.63 oz) of ground coffee extracted into about 40 ml (2 fl oz; two shot glasses). Thus, a "double ristretto" consumes the same amount of coffee beans but fills only a single shot glass.

Source: Wikipedia