I have a noun that consists of two words ("impact parameter") that I am trying to turn into a compound adjective to describe a certain type of collision ("high impact parameter collision"). Where, if anywhere, should the hyphens go on this phrase? The two choices I can't decide between are:

  • high-impact parameter collision
  • high-impact-parameter collision

There may be some obscure rule for this, but if I were you, I'd trust my intuition a tiny bit more.

"High" here modifies "impact," not "parameter." However, this only becomes manifest if you join them together by using a hyphen.

That said, yet another hyphen would negate the effect, rendering the meaning of the phrase vague once again.

I would therefore vote for

high-impact parameter collision

I hope this helps.

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  • 1
    high modifies "impact parameter". I'm not talking about parameters with high impact, I'm talking about collisions with high impact parameters. "Impact parameter" refers to one idea. – NeutronStar Mar 29 '17 at 18:50
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    @Joshua I think that's only clear if you go with "high impact-parameter collision". Leave the noun as a compound noun and don't hyphenate to make the adjective. An alternative for academic writing is to define a new term or acronym once, clearly, then only use that. Going with "high-IP collision" might resolve the concern while preserving readability. – Mathily Mar 29 '17 at 19:17
  • @Joshua: Whatever floats your boat, dude! – Ricky Mar 30 '17 at 0:39

Does the parameter collision have high impact?

  • I might use high-impact parameter-collision

Or do the parameters have high impact and they then collide?

  • I might use high-impact-parameter collision

Or is the impact parameter collision high?

  • I might use high impact-parameter-collision

Or are the impact parameters high and they then collide?

  • I might use high impact-parameter collision

A lot of this comes from personal preference. Perhaps it should all be rephrased for greater clarity

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  • Yes; stacking modifiers quickly leads to inevitable clunkiness and frequent ambiguities. – Edwin Ashworth Mar 29 '17 at 22:37
  • The planets have an impact parameter that is high when they collide. – NeutronStar Mar 30 '17 at 14:45

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