I was filling out a form and I saw:

Approximate course start date

and not

Approximated course start date

if I used the word "estimate" wouldn't I have to use it in the past if so why do we use "approximate" in the present and not in the past?

  • Approximate doesn't belong to the present, any more than estimated belongs to the past? Here, "approximate" defines the thing; "approximated" explains how the thing was derived. Does that make sense? Considering the difference between (any)ate and (any)ated how much, to you, does that final "d" matter? Commented Jan 11, 2021 at 23:30

3 Answers 3


Because approximate is an adjective here. https://dictionary.cambridge.org/dictionary/english/approximate

The applicant may not know the exact date that the course will start - the date may not even have been published yet - but they know that it will be in a certain time frame. They are not estimating the date in the sense of calculating it from known data.

  • 1
    This is most likely the correct interpretation. The labels on a form are normally noun phrases, not complete sentences. You wouldn't expect to see a verb there.
    – Kevin
    Commented Jan 11, 2021 at 7:56
  • 5
    Worth pointing out that "approximate" the adjective is pronounced differently (the last vowel becomes a schwa) to "approximate" the verb. It's the same pattern for "estimate" the noun vs "estimate" the verb.
    – Muzer
    Commented Jan 11, 2021 at 11:42
  • The final vowel in the noun usage of "estimate" is a short "i", not a schwa. English pronunciation is tricky and written language can be very unhelpful.
    – JonathanZ
    Commented Jan 11, 2021 at 15:10
  • 1
    @JonathanZsupportsMonicaC: No, it is pronounced as a schwa, at least in the common UK and US dialects. Some dialects may have short "i" though - where are you from?
    – psmears
    Commented Jan 11, 2021 at 16:11

Both approximate and estimate can be used in two different ways. They both can be used as verbs, and are pronounced with a "long a" in the last syllable in that case.

Approximate can also be used as an adjective, and the last syllable is pronounced like a "short i" in this case.

Estimate can be used as a noun, and the last syllable is a pronounced with a "schwa" for this.

So if you want to use a form of estimate as an adjective, as you are, you have to use the past participle of the verb, i.e. estimated. Note that the pronunciation keeps the "long a", which hints that it's the verb form that is the source.

I can't see any logical reason to explain the difference, or any wider principle at play. I think it's just one of those things you have to learn specifically.

You could argue that the past participle of approximate should also be able to be used as an adjective, and that one should be able to say "the approximated date". This isn't exactly incorrect, but it does sound a bit stilted, and puts a lot of emphasis on the act of approximation. If I try to come up with a scenario where it'd be used the best I can come up with is e.g. "There were many factors involved in approximating the date for the harvest to start, and the approximated date is subject to further updates, depending on the weather." Usually people would just say "the approximate date".

(Source: Wiktionary: approximate, estimate.)


Because approximate as a transitive verb has a slightly different meaning. Using the definition from here


  1. To come close to; be nearly the same as: This meat substitute approximates the real thing.
  2. To bring near.
  3. To bring together, as cut edges of tissue.

So approximated does not have quite the same meaning as estimated or expected both of which you could use here.

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