Is the following sentence correct, and is its use of the semicolon correct? Note that the use of the word 'concurrency' is meant to indicate a computer science term.

A host of design issues are encompassed by concurrency; that of interaction amongst processes, the sharing and competition for resources, the synchronisation of the activities of multiple processes and the allocation of processor time to processes.

  • 2
    Personally, I would use a colon there coming before details or a list.
    – Henry
    Feb 19, 2012 at 0:01
  • 2
    Not using a serial comma here is a crime.
    – tchrist
    Feb 19, 2012 at 0:19

1 Answer 1


I think I'd use a colon or a dash instead of a semicolon. It's being followed by a list, after all; but it's not wrong, just not optimal.

As for the list itself, it's not parallel enough. Parallel constructions reduce understanding effort and make things clearer to listeners and readers.

The four things in the list need to have more parallel structures, and I'd reduce them to three, putting the first and last together, and I'd use NP compounds instead of prepositional phrases, which are notoriously subject to attachment ambiguities

  • interaction and allocation of processor time among processes,
  • sharing and competition for resources,
  • synchronisation of multiple process activities

(btw, use among, not amongst, unless you're being consciously archaic, and there's no reason to use Passive in the main clause). So the "improved" sentence would be

Concurrency encompasses a host of design issues -- interaction and allocation of processor time among processes, sharing and competition for resources, and synchronisation of multiple process activities.

  • @JohnLawler, I agree with your parallelism comment and I believe the 4th list item to be redundant, however I think it is subsumed by the third, i.e., processor time is a resource. When I read 'interaction amongst processes' I interpreted that to mean communication-type interactions. One might also say that the proposed improvement is a bit ambiguous with respect to the elaboration of the first list item. Is it: "Interaction of processor-time, and allocation of processor-time among processes" or is it "interaction among processes and allocation of processor-time among processes?"
    – Jim
    Feb 19, 2012 at 0:16
  • But what if you’re unconsciously archaic? If a native speaker naturally and unselfconsciously just happens to say amongst, whatever can be wrong with that? BTW, his lack of a clear serial comma makes the last component confusing; I’m glad to see you restored it.
    – tchrist
    Feb 19, 2012 at 0:20
  • 1
    John, nice answer. Very fast too! Feb 19, 2012 at 0:40
  • 2
    +1 - in such constructions, a list of exactly and only three items is always to be preferred. Feb 19, 2012 at 0:54
  • Has English writing style changed since the 1980s? I am sure that when I was taught style for technical writing, it would always always be a colon for lists, and semicolons were only for dependant clauses.
    – Warren P
    Feb 19, 2012 at 4:23

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