# Use of a hyphen with the word "based"

I'm checking a technical paper submission and came across the phrase

We propose spherical Gaussian based approximations to calculate this analytically.

and wondering if this needs a hyphen or not. I'm inclined towards

spherical Gaussian-based

but could it also be

spherical-Gaussian-based

which is what some of the other questions on hyphenation here are based on.

• Please provide the complete sentence that contains the words you are asking about. Commented Nov 10, 2014 at 7:03
• Is the Gaussian spherical? spherical-Gaussian-based approximations. Are approximations spherical? spherical Gaussian-based approximations. If it is your proposition that a spherical fellow named Gaussian did base his approximations in order to calculate this analytically (unlikely, but hey), then spherical Gaussian based approximations. Commented Nov 10, 2014 at 7:45
• english.stackexchange.com/questions/100818/… Commented Nov 10, 2014 at 8:10
• Also related to english.stackexchange.com/questions/51665/… Commented Mar 29, 2017 at 10:21

In most U.S. English style guides, the decision about whether to double- or single-hyphenate a phrase such as "spherical Gaussian based approximations" rests on whether the first word in the string attaches primarily to the noun or primarily to the modifier closer to the noun. In other words, if you are talking about Gaussian-based approximations that are spherical, you would normally use a single hyphen:

We propose spherical Gaussian-based approximations to calculate this analytically.

But if you are talking about the kind of Gaussian basis (namely, spherical) that underlies the approximations, you would normally use two hyphens:

We propose spherical-Gaussian-based approximations to calculate this analytically.

I don't know anything about this area of physics (or mathematics), but it seems to me likely that the first of these associations is the one that the writer intends here, which would make the single-hyphen approach suitable.

• It's actually related to lighting in a real-time graphics applications. Judging by other phrases in the paper, these are Gaussian's of a spherical nature. Thanks for your input.
– psd
Commented Nov 10, 2014 at 8:43
• According to this answer, "spherical Gaussian based" is another acceptable alternative to "spherical-Gaussian-based". Commented Dec 14, 2023 at 8:09
• @MateenUlhaq: The answer that your comment links to (which was posted in 2011) does indeed say that leaving the phrase open is an option—and the question poster accepted that answer. A year later, however, Peter Shor posted a different answer, recommending the use of an en dash in the particular situation involved there (a two-word proper name combined with the word "based"). His answer reflects the relevant guideline in The Chicago Manual of Style —and not surprisingly, it has received 19 upvotes over the years to the accepted answer's 5, despite appearing a year later. Commented Dec 20, 2023 at 18:05