PTP-SD is a type of algorithm.

PTP stands for "probabilistic tree pruning" SD stands for "sphere decoding"

PTP-SD is a type of algorithm that uses PTP with SD.

My question is about the use of the hyphen here. In the paper I am currently editing, the author has written the following:

"Increasing radii algorithm (IRA) [10] and probabilistic tree pruning with sphere decoding (PTP-SD) [11] reduces the complexity by adopting the different radii in each layer instead of fixed radii used in the literature."

In such examples, the spelled out form contains no hyphen. Is this okay? Should there be one? If so, where should it go? Why should only the abbreviation contain a hyphen but not the spelled out form?

  • 1
    This seems entirely acceptable. For comparison, consider the acronym CD-ROM. Jun 11, 2014 at 19:05

3 Answers 3


It seems to me the hyphen is not meant to represent the word "with", but rather to separate the two parts of the acronym, PTP and SD. This separation indicates that PTP-SD is made up of its two parts, and it does a better job of representing the algorithm than combining everything into one big PTPSD.

Similarly, consider the acronym CD-ROM. The hyphen here is standard, and denotes that this is a Compact Disc which uses Read Only Memory. Since ROM is itself an acronym, putting the hyphen there makes it clear that CD-ROM has something to do with ROM and isn't just an entirely new acronym.

  • The hyphen in CDROM also aids in pronunciation; it emphasizes that "see drom" would not be appropriate.
    – Barmar
    Jun 15, 2014 at 3:51
  • @Barmar Good point. Jun 15, 2014 at 16:54

I'd say the hyphen refers to the "with" in the spelled out form.

Usually, acronyms are short (2-4 letters). In this case, the term "PTPSD" does not convey its intended meaning i.e. probabilistic tree pruning sphere decoding which makes no sense.

Also, the acronym can be split up into two terms by themselves: probabilistic tree pruning, which is one thing, and sphere decoding, which is another. Thus, a hyphen is used to ensure that the two things are recognized as two separate entities which form one other when linked together.

For example, when using an acronym such as NATO, no hyphen is used as it is merely one entity (North Atlantic Treaty Organization). But when another entity is introduced, a hyphen is included, leading to the fictional SEA-NATO (South-East Asian North Atlantic Treaty Organization).

However, note that not every "with" has to be replaced by a hyphen. Basically, the rule of thumb is to follow whoever coined the acronym.


This analysis does not cover rules on hypheting acronyms for a line-break (the acronym wraps around from one line to the next

  • 1
    Hello, Benjamin. OP does not (and should) give a reference validating the form PTP-SD, and the example given unhelpfully uses, as you point out, a line-break. If you have an answer to the question (with authoritative reference), please answer; this is a comment as it stands (and shouldn't be submitted in 'answers'). We've all had to negotiate the 50-rep hurdle. // Please note that the prevailing usage (at least on ELU) of 'acronym' entails 'must be pronounced as a word') (so NASA but not initialisms such as BBC). Apr 16, 2021 at 13:03

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