- 1 quickly Don't drive so fast! How fast were you going? I can't go any faster. The water was rising fast. Her heart beat faster. (formal) Night was fast approaching. a fast-flowing stream Which Word?quick / quickly / fast Quickly is the usual adverb from quick:I quickly realized that I was on the wrong train. My heart started to beat more quickly. Quick is sometimes used as an adverb in very informal language, especially as an exclamation:Come on! Quick! They’ll see us!Quicker is used more often:My heart started to beat much quicker. The quicker I get you away from here, the better. Fast is more often used when you are talking about the speed that somebody or something moves at:How fast can a cheetah run? Can’t you drive any faster? You’re driving too quickly. There is no word fastly.
- 2 in a short time; without delay Children grow up so fast these days. Britain is fast becoming a nation of fatties. The police said that they had reacted as fast as they could. firmly
- 3 firmly; completely Within a few minutes she was fast asleep (= sleeping deeply). The boat was stuck fast (= unable to move) in the mud. There is no noun related to fast. Use speed in connection with vehicles, actions, etc.; quickness is used about thinking. Word Originadverb Old English fæst ‘firmly fixed, steadfast’ and fæste ‘firmly’, of Germanic origin; related to Dutch vast and German fest