Let me use an example to clarify:

Puer librum legendum habet

Very, very literally, this would be:

The boy has a book going to be read

This has the sense of happening in the future and passivity, and acts as a participle (as far as I can tell), but for some reason this isn't the translation. Instead, future passive participles carry a sense of necessity:

The boy has a book having to be read

Where did that come from?

  • 1
    I don't know. It makes just as much sense to me as using the to-infinitive the way we do in English: "the boy has a book to read."
    – Asteroides
    Mar 3, 2016 at 23:27
  • @sumelic I was taught that the Latin oddity is where the English one came from.
    – Nic
    Mar 3, 2016 at 23:30
  • Is it? Hmm. I don't see why that would happen, but I guess it is possible.
    – Asteroides
    Mar 3, 2016 at 23:30
  • @sumelic Admittedly I don't know for a fact, but again, that's what I was taught. Or at least that's what my annoyed teacher said when I kept bugging him about it.
    – Nic
    Mar 3, 2016 at 23:31
  • 1
    It's an interesting idea anyway. I just don't know anything about it, and it seems odd to me. While looking for more information, I found a source that mentions a hypothesis that the English progressive came from Latin influence which I never heard of before: homes.chass.utoronto.ca/~cpercy/courses/6362-lamont.htm
    – Asteroides
    Mar 3, 2016 at 23:37

2 Answers 2


I see now that some people call this a "future passive participle", but it is conventionally called a gerundive. So I wouldn't think of "going to be read" at all if I were to translate it.

A sense of prediction or obligation is inherent in any gerundive. The most literal translation is as follows—by most literal I mean the one that works in most situations, especially in a neutral context, and that is the least dependent on context in general:

Puer librum legendum habet. — "The boy has a book to read."

In English, to + infinitive can express that something will happen or should happen. Although this English construction and the gerundive are not related, they both happen to reflect this double modality: probability (will happen) and desirability (should happen). Necessity can be a kind of desirability ("this room needs to be cleaned") or a kind of probability ("random DNA mutations are necessary for cancer to develop"). I beg your forgiveness for quoting myself:

This is a complicated issue, and one that is still not fully understood by linguists, or so I believe. In short: there is a tendency in many languages for words to shift in meaning between probability and desirability. This tendency is apparently strongest in certain verbs that are used without specifying who the judge is, which includes passive verb forms.

Why do we say “was supposed to” for “should have”?

The gerundive always has this double, shifting connotation. In some contexts one kind of modality prevails, in other contexts the other. And with dominant gerundives, such as in gerundive constructions, neither seems to prevail:

Floribus capiendis Eurydice mordetur serpente.

  • As a side note, I'd say that it's a prerequisite for the "necessity for cancer" meaning, not a possibility
    – Nic
    Mar 4, 2016 at 0:54
  • 1
    @C.M.Weimer: Why do you call it passive? I punish the boys: agent I, patient the boys. There were no boys to punish: the phrase to punish modifies no boys, but the agent is not the boys: no agent is mentioned. It is the other way around: the boys are the patient. So the predicate frame is reversed between subject and object, as it happens with passive verbs. That's why there were no boys to punish means the same thing as there were no boys to be punished. In the construction I was to punish the boys, the phrase to punish is active (different predicate frame).
    – Cerberus
    Mar 4, 2016 at 1:00
  • @QPaysTaxes: But it has to do with probability, rather than desirability, right?
    – Cerberus
    Mar 4, 2016 at 1:01
  • @C.M.Weimer Wait for the magic blue link to appear, or a magic blue diamond
    – Nic
    Mar 4, 2016 at 1:05

I'm not entirely sure, but it could be that the future passive participle simply originated as a shorthand/alternate translation for the passive periphrastic, which is defined to have a sense of necessity. In your example, Puer librum legendum habet, you could just as easily have extended it to Puer librum quem legendum est habet, meaning "The boy has a book which has to be read," and changing it to the passive periphrastic. The future passive participle seems to follow naturally as a shortening of this form.

  • 1
    I like this explanation, but it seems to me that the periphrastic would have grown out of the participle, not the other way around. Then again, I have no idea either way, so no complaint from me.
    – Nic
    Mar 3, 2016 at 23:59
  • Well yeah, I was thinking the same thing - either one could've come first
    – Nick
    Mar 4, 2016 at 0:09
  • For what it's worth, your Latin should probably be Puer librum legendum habet and Puer librum quem legendum est habet. But I like your thinking! Mar 20, 2016 at 1:04
  • Oops - managed to forget the gender. Thanks for pointing it out.
    – Nick
    Mar 20, 2016 at 1:31

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