In dictionaries, the adjectives 'fast'/'slow' are usually defined such that it makes sense for them to be applied to the actual moving or otherwise action-performing subject, such as for example here at Dictionary.com:


adjective; faster, fastest.

  • moving or able to move, operate, function, or take effect quickly; quick; swift; rapid ...

I wonder whether it is correct to use them to describe not the subject, but its speed instead. If I think about the speed as a measurable quality, it makes sense for it to be 'higher' or 'lower', but since the speed itself is not the one performing the action, does it make sense to describe it with an adjective defined, for example, as above? In other words, the car is fast, its speed can be high, but is it correct to describe its speed as fast also?

In a broader view, similar questions could be posed about 'heavier weight', 'cheaper price', etc.

To articulate my questions more precisely:

1/ Is 'fast speed' technically correct, i.e. would a conscientious editor allow it?

2/ If not, is it at least natural enough, i.e. would a native speaker use it?


1 Answer 1


Google 2-grams for fast speed / high speed / slow speed / low speed show that 'fast speed' and 'slow speed' are actually used, but are not as idiomatic as the expressions 'high speed' and 'low speed'. Many would indeed say that 'fast speed' and 'slow speed', invoking speed twice, are tautologous and therefore stylistically poor.

However, since speed is almost synonymous with setting when considering say kitchen devices (and compare with a ten-speed racing bike), there is an increasing usage with examples such as that given in Collins CoBuild (the second below):

slow [adjective]:

Something that is slow moves, happens, or is done without much speed.

  • The traffic is heavy and slow.
  • Electric whisks should be used on a slow speed.

But 'the car's speed is fast' is certainly better avoided.

  • Thank you; the note about 'speed' being used in the sense of a 'setting' is particularly insightful.
    – mzi
    Aug 4, 2020 at 11:29

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