Learn English – “separated by”, “separated with”, or does it not matter

by-withprepositionsword-choice

I'm describing how you write something down (specifically, an array initializer in JavaScript, but that's not important), and find myself intrigued by the choice of using "separated by" vs. "separated with." I wonder if there are rules, or whether it doesn't really matter which you use.

As a native English speaker (mostly of American English but influenced by British English), my largely unschooled instinct is that "separated by" is more of an observation of fact ("As we can see in the diagram, the entries are separated by commas"), and that "separated with" is more related to an instruction ("When writing…put the entries between the square brackets, separated with commas")… I think part of the reason I feel that tug toward "with" is that I'd definitely use "with" in the imperative sentence "Separate the entries with commas."

Is there language logic to back that up? And/or is my unschooled instinct simply wrong? 🙂

In this case, I'm primarily interested in informal but professional American English usage.

Best Answer

In a passive construction with a participle like separated, by and with have different functions.

  • by marks an agent phrase: The fighters were finally separated by the referee.
  • with marks an instrumental phrase: The fighters were finally separated with a crowbar.

When you're talking about metaphoric separation -- item boundaries in a left-to-right line -- you have the option of treating the "separator" either as an agent itself, or as a tool (of another agent).

Interestingly, this is the same range of meanings as the agentive -er suffix:
a typewriter is an instrument, but a ghostwriter is a human, and therefore an agent.

  • The entries are separated by commas is the agent interpretation,
    a passive version of Commas separate the entries.

  • The entries were separated with commas is the instrument interpretation,
    a passive version of Indef separated the entries with commas.

Note the different tenses required above; being separated is either an event or a state. Permanent states normally take present tense (My car is red even though it's been red for 5 years). Events can be located on the time continuum, usually in the past tense. So past tense is likely to signal reference to an event, and present tense to a state.

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