I was just wondering what the difference is, if any, between these two sentences:

  1. Instruments are to be machined.
  2. Instruments have to be machined.

I would be highly glad if anyone helps by giving intellectual reasoning of the difference.

What’s the difference, if any, between saying are to be in (1) and saying that they have to be in (2)? Or do they mean exactly the same thing?

Do (1) and (2) mean the same thing as any of these following versions?

  1. Instruments are going to be machined.
  2. Instruments will be machined.
  3. Instruments should be machined.
  4. Instruments must be machined.
  5. Instruments ought to be machined.
  6. Instruments need to be machined.
  7. Instruments will need to be machined.
  8. Instruments are going to need to be machined.
  • 1
    In the sentences both constructions suggest similar meanings, that is something must be done. Are to be (more formal) here is a more general statement, it suggest that something will have to take place sooner or later. Have to be refers to something that has to be done soon, an order. Note that, however both constructions may be used to convey the same meaning when you want to express urgency like , "The plan is to be (has to be) approved before tomorrow" .
    – user66974
    Commented May 15, 2015 at 6:39
  • @Josh61 I would suggest that the first one could indicate the instruments are awaiting machining - the decision to machine them already having been made. However the second might be used to advise someone that it is necessary for them to be machined. There are all kinds of possible meanings here, some of which call for the first, some for the second sentence, for idiomatic use.
    – WS2
    Commented May 15, 2015 at 8:12
  • Thank you very much everyone for the logistics u are discussing here. I am feeling more cheerful now. Commented May 15, 2015 at 8:15
  • Related.
    – tchrist
    Commented Feb 25 at 17:42

2 Answers 2


"Instruments are to be machined" suggests that the machining is done as some form of duty or agreement, or as part of a job. You'd likely hear it from a boss or some kind of authority figure who is instructing an employee or someone over whom he or she has power. "Are to be" doesn't have the connotation of necessity that "have to" has. It simply suggests that this is the way things are done, not because they must be, but because that is what has been decided or scheduled.
"Instruments have to be machined," on the other hand, suggests that there is some reason, aside from someone's preference or decision, that the instruments must be machined--for example, if they're not, they'll stop working.

In short, the first suggests that the instruments should be, or are intended to be, machined, whereas the second suggests that the instruments must be machined.

  • I think one could compile a range of contexts some of which call for one and some for the other. It would be an interesting exercise for a non-native speaker. It is these kinds of subtleties that even the most competent non-natives sometimes get wrong.
    – WS2
    Commented May 15, 2015 at 8:15

Both have similar meanings with only a subtle difference.

"Are to be" is another way of saying "should be", which is instructive (passive command) rather than urgent and forceful.

On the other hand, "have to be" is like "must be", which implies necessity and requirement with more urgency than "are to be".

  • Thanks for the intellectual answers.Your answer really helped me to clear the subtle difference between the two. Commented May 15, 2015 at 7:52

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