Prerequisite describes something that must exist before another thing. Is there a word that describes an opposite, that is, something that is made possible because of the existence of another thing?

For example, in Carl Sagan's famous quote "If you wish to make an apple pie from scratch, you must first invent the universe", inventing the universe is a prerequisite of making an apple pie from scratch. Is there a word that works when we switch those two subjects: making an apple pie from scratch is a(n) ______ of inventing the universe?

I know that I can rephrase the sentence, or use multiple words to express the meaning, for example, "making an apple pie is one of the things I can do after inventing the universe". I can also use a made up word like postrequisite (although that exact example may not fit, as I understand it means something that must be done afterwards). I would like to know if there is one word, that is used widely, that means the same.

  • Wouldn't the opposite be something that is then made impossible? These are still prerequisites. Enabled?
    – Mazura
    Feb 15, 2016 at 3:03
  • @Mazura There are many different ways to construct opposites, or antonyms. I agree "opposite" is imprecise, so I provided some examples. Another "opposite" to prerequisite is the made-up postrequisite (something that must be done afterwards). Feb 15, 2016 at 3:07
  • Ah, I got ya. I have a personalized Windows disk. It has an extra folder called run.it.after (stuff that cleans up the install).
    – Mazura
    Feb 15, 2016 at 3:13
  • Precursor would work here.
    – user116032
    Feb 16, 2016 at 3:10

15 Answers 15


What about dependency?

de·pend·ence n. 4. The state of being conditional or contingent on something, as through a natural or logical sequence. “The dependency of an effect upon a cause.”

Dictionary.com (cf. Random House Unabridged Dictionary)

Or, comparing the respective definitions found in Webster’s 2nd:

pre·req·ui·site (prē·rĕkʹwĭ·zĭt), adj. Required before; necessary as a preliminary to a proposed effect or end; essential as a condition precedent. n. 1. Something required beforehand; something necessary to an end or effect; a condition precedent; as, the prerequisites of freedom. …

de·pendʹen·cy (dē·pĕnʹdĕn·sĭ), n. 1. State of being dependent. = DEPENDENCE, 4, 5. 2. That which depends; that which is attached to something else as its consequence, subordinate, annex, etc. de·pendʹence (dē·pĕnʹdĕns), n.4. State of being influenced and determined by, or of being conditional upon, or necessitated by, something else; as, the relation of an effect to its cause is one of dependence. 5. State of depending, or being subject; specif., subjection to the direction or disposal of another or others; inability to … provide for oneself; …

  • 6
    Do you mean dependant instead? Dependency is often used to express the inverse relationship, i.e. A is a dependency of B, B is a dependant of A. Feb 15, 2016 at 8:33
  • 1
    @congusbongus - From a linguistical point of view, the dependency is the state of being dependent. However, in computer science, the word often describes an A-B relationship, without a clear identification of which is the prerequisite.
    – Graffito
    Feb 15, 2016 at 8:47
  • 6
    @congusbongus: I think you have jumped the gun on accepting this answer. And I'm honestly surprised it has the most upvotes, given the number of programmers who also frequent this site. Your comment can be strengthened from "often" to "almost exclusively", at least in computing. Dependency is in fact used interchangeably with prerequisite when talking about software requirements.
    – John Y
    Feb 15, 2016 at 13:28
  • I agree this is backwards. "the x of y" means "y's x". "The dependency of an effect" means the effect has the dependency of its cause. The cause is a dependency of its effect. You can substitute the word "prerequisite" without changing its meaning.
    – MichaelS
    Feb 16, 2016 at 0:42
  • I think dependency and dependant are both backwards. The word dependee would fit, if it were a real word.
    – Ed Griffin
    Feb 19, 2016 at 10:33

You could consider using a "possible outcome". Outcome means:

The way a thing turns out; a consequence: 'it is the outcome of the vote that counts'

[Oxford Online Dictionary]

Your example:

Making an apple pie from scratch is a possible outcome (one of possible outcomes) of inventing the universe.

  • This is as close as it gets, I think, with some synonyms: possible outcome, potential result, etc. Feb 15, 2016 at 8:29

I don't believe there is a widely used word that means what you want. For maximum clarity and unambiguousness, just use a phrase.

If you absolutely must use a single word, you could try enablement:

[From TheFreeDictionary:]

n. 1. The act of enabling, or the state of being enabled; ability.

This word does have established uses other than your intended meaning, but if you craft your sentence carefully, you may be able to provide enough context for the reader to get what you mean.

  • "Enablement" is nice as a complement to "requirement" (which is in turn a synonym of "prerequisite"). Thus, "A is an enablement of B" if and only if "B is a requirement of A".
    – Paul Wintz
    Oct 20, 2022 at 6:13

I don't think a strict opposite of pre-requisite exists in English but considering pre-requisites and preconditions are synonymous, how about postcondition?

In computer programming, a postcondition is a condition or predicate that must always be true just after the execution of some section of code or after an operation in a formal specification. Postconditions are sometimes tested using assertions within the code itself. Often, postconditions are simply included in the documentation of the affected section of code.


Although it is primarily a computer term, it may fit your sentence well, if you offer it some flexibility.

Making an apple pie from scratch is a postcondition of inventing the Universe.

It tends to imply that "if the Universe is created, the apple pie must be made from scratch."

Ngrams indicate that it is a fairly popular term since the late 1970s.

  • I don't think this is the same. With the OP, we're not saying apple pies must exist in any universe. We're just saying an apple pie can't exist without the universe first existing. A postcondition says kind of the opposite: an apple pie might exist without a universe, but the presence of a universe necessarily means there are apple pies. universe -> pie instead of pie -> universe.
    – MichaelS
    Feb 16, 2016 at 0:28


(of an action, process, or argument) require as a precondition of possibility or coherence.

"his relationships did not permit the degree of self-revelation that true intimacy presupposes"

synonyms: require, necessitate, imply, entail, mean, involve, assume

"this presupposes the existence of a policy-making group"

- source

Other possibilities include:

  • requires
  • necessitates
  • entails

Use any of the options below (followed by on/upon) to describe something made possible by something else:

  • contingent
  • dependent
  • conditional
  • I think this is a strong fit. Making an apple pie from scratch presupposes inventing the universe. Feb 15, 2016 at 18:54
  • 1
    +1 for contingent which leads to is contingent on/upon in OP's case.
    – Jim
    Mar 6, 2016 at 21:42

Use the root word of prerequisite, require.

Making an apple pie requires (first) inventing the universe.

You could also just use prerequisite in a wordier fashion:

Making an apple pie has the prerequisite of inventing the universe.

Alternately, "only possible" or "can only be accomplished" would make sense here.

Making an apple pie is only possible after inventing the universe.
Making an apple pie can only be accomplished after inventing the universe.

Random note: for some reason, trying to quickly type "apple pie" constantly results in "applie pie". Brains are weird.

  • The OP looks for exactly the opposite, so your answer is not useful. Feb 15, 2016 at 9:28
  • @rexkogitans: The OP asks how to say making apple pie is possible because of the invention of the universe. If inventing the universe is a requirement, then making an apple pie has that requirement, or requires said invention. It may not be the best possible word choice, but it does exactly what is asked for.
    – MichaelS
    Feb 16, 2016 at 0:17
  • Oops, forget about my comment... sorry... I upvote it... Feb 16, 2016 at 8:00


from Wiktionary: something which occurs a fortiori, as a result of another effort without significant additional effort. Finally getting that cracked window fixed was a nice corollary of redoing the whole storefont.


Such a thing is sometimes called a postrequisite or post-requisite of the thing(s) it depends on. In DITA, for example, a post-requisite (element <postreq>) "describes steps or tasks that the user should do after the successful completion of the current task." (But in some DITA contexts I think it is understood more as things that the user can do, not necessarily things that the user should do.)

But this word is essentially newly coined, as far as I can tell.

  • I agree that postrequisite, like the similarly non-standard prepone, can be easily understood, but I'd prefer something that is used more widely, something more standard. Besides, it has a slightly different meaning - "that which is required to be done after" - than what I want. Feb 15, 2016 at 3:10
  • Why don't programmers call it dependent?
    – Mazura
    Feb 15, 2016 at 3:16
  • @congusbongus: My understanding is that a postrequisite is not something that is required to be done after, in the sense that it is required. It is something that can only be done after its prerequisite, but it is not necessarily required (mandatory). In this it is not exactly a mirror of prerequisite. IOW, postrequisite is precisely what you said in your question: "one of the things I can do after" - the operative word being can, not must.
    – Drew
    Feb 15, 2016 at 3:18
  • This smells like the elusive COMEFROM command that never made it into Radio Shack BASIC. In my admittedly limited experience, many programmers have been accused of using English, but actual convictions have been infrequent. Grmpf. ;-).
    – Rob_Ster
    Feb 15, 2016 at 3:35
  • 1
    It's possible that some people use postrequisite to imply can, rather than should or must, but this is definitely uncommon. If you Google for postrequisite, you will see that most people take it to mean something that isn't optional.
    – John Y
    Feb 15, 2016 at 13:59

The word consequence fits nicely into the reversed Sagan quotation. You could also try sequel for this particular context.

Since prerequisite can also suit up and play as an adjective, an appropriate opposite number could be attributable.

  • 2
    I disagree that consequence fits nicely. If B is a consequence of A, that means B necessarily follows from A. The question is: what's a word that means B can follow from A.
    – John Y
    Feb 15, 2016 at 5:31

I kind of think the word byproduct works in the scenario you paint. It's not precisely what you describe, but definition #2 I think is awfully close.

by·prod·uct | ˈbīˌprädəkt | noun | 1. something that is produced during the production or destruction of something else. 2. something that happens as a result of something else.



Use antonyms for prerequisite: 1optional, 2unnecessary, 3voluntary, 4inessential

A and B are possibilities and/or 1234.

A is 1234 to/for B.

A need not be 1234 to B. [can be or not be by choice]

I also had this thought:

You want - A is, hence B. Eg. "I have a digestive system, hence I can eat".

To be the opposite of - A is, thus B. Eg. "I am hungry, thus I must eat".

  • 2
    Hi, Grammaticus, do you think optional or others would fit in the blank of the Original Poster's example sentence? We need a noun, not an adjective.
    – user140086
    Feb 15, 2016 at 9:45

Product Of or Derived From

This implies a connection between the two but maybe that forms the requisite.


You could use the terms from mathematical logic: necessary condition and sufficient condition. The following statements would both be correct and both say the same thing:

Inventing the universe is a necessary condition for making an apple pie from scratch.

Making an apple pie from scratch is a sufficient condition for inventing the universe.

What that last statement is saying in other words is: if you have indeed made an apple pie from scratch, then this is sufficient information to know that that you have also invented the universe.



In software, the terms that relate to your question are preconditions and postconditions. Meaning those things that are true before (upon entry to a procedure) and those things that are true after (upon exit from a procedure).


Successor: a person or thing that succeeds or follows.

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