...to the north the impenetrable forests of Gurgan and the Elburz range, to the south the fastnesses of Persia itself, a province which Artaxerxes III, contemporary of Philip, had never visited during his reign...

I've never seen 'fastness' used like in the quote, but what's meant seems to be (approximately) the same as 'fast'. Dictionaries corroborate this (edit: this was mistaken; actually, 'not exactly', or 'no they don't')

What is the difference between 'fast' and 'fastness'? And, come to think of it, what about 'fort' and 'fortress'? Is there a subtle rule here?

(edit): I mean 'fast' in this sense: https://en.wiktionary.org/wiki/fast#:~:text=prypyn%C3%BDty%20vohon%CA%B9)-,Etymology%202%5Bedit%5D,-From%20Middle%20English

the sense "fortress, enclosure"

(edit 2): this may not be a strictly 'English', ie Modern English, question. I may close it soon.

(edit 3): I frankly don't know why I thought that 'fast' as a noun meant something like 'fortified/secure area'. Maybe I once saw it intended an adjective in a grammatically ambiguous context. In any case, I've answered my question.

  • 2
    the fast of Persia itself would be ungrammatical, since fast is not a noun—except when used for a period of time when you stop eating. Feb 20, 2023 at 19:39
  • I'm about 90% sure this is a typo for "vastness."
    – alphabet
    Feb 21, 2023 at 18:49

2 Answers 2


They don't mean the same thing. In this context, one is a noun and the other an adjective. A "fastness" is a thing which is fast.

"Fast" in this context means secure or fixed, as in "hold fast", "held fast", and describing attachment hardware as "fasteners".

According to dictionary.com, "fastness" can also relate to velocity, but that isn't how it's being used in the context of the quotation.

[Edit : I didn't spell it out at first, as I was trying to avoid stepping on user888379's toes, but it looks like it's worth adding that the quotation in the question was referring to Persia as being secure (from invasion) as it was heavily fortified.]

  • fastness is not a thing, it is a quality of speed.
    – Lambie
    Feb 20, 2023 at 20:31
  • @Lambie - Did you follow the link? (We both know the answer.) Feb 20, 2023 at 20:45
  • @Lambie - I let my annoyance get ahead of my keyboard, there. Apologies. You're right that fastness can relate to speed, but that's not its only meaning. I don't think it fits the context in the question - but let me know what you'd understand by "the fastness of Persia" in relation to speed. [Note : I'm already there on the idea that "I ran" would be a good answer to that...] Feb 20, 2023 at 20:54
  • 1
    For the Persia thing, it's forts, not speed, of course. :) Those things can be called fasts or fastness, which I admit I didn't know prior to see the dictionary entry.
    – Lambie
    Feb 20, 2023 at 21:12
  • @Lambie - Thanks for coming back. I wouldn't have cited dictionary.com if I'd read their entry for "fast", which only just touched on the idea of attachment hardware. Feb 20, 2023 at 21:21

I'm pretty sure the fastness here is the second definition in the link:

2 a : a fortified or secure place b : a remote and secluded place

  • 1
    Yes, this does make perfect sense in this context.
    – Lambie
    Feb 20, 2023 at 20:31

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