In math, we use the term series a lot, and there are many types of series.

How should I craft my sentence when I have three different ones in mind to talk about? Should I settle down for a less mortal alternative of “list of series” or something like that?

The existing question on The possessive and plural forms of “series” suggests the usage of series’. But is that all?

If that’s the only solution, then could you please explain the usage of apostrophe symbol at the end? Is that a plural marker or a possessive marker, or both?

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    I fail to see where in the linked question it suggests that the plural of series were series'. It only does so for the possessive. Wiktionary, Merriam-Webster, and the Free Dictionary all say that the plural is "series". You yourself have just written, "I have 3 different series in mind". I am not sure what questions are still left. – RegDwigнt Feb 23 '12 at 15:37
  • @RegDwightѬſ道 Moreover, the true reason for why the plural and/or possessive of nouns like species and series must be invariant is quite interesting, and merits discussion. See my comment to John. – tchrist Feb 23 '12 at 15:49
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    What a dumb reason to close a question. Stack Exchange is a reference. Whether it was first is no impediment to being best. In fact, the top two results googling "plural of series" are stack exchange articles. Except now one of them can't be given new answers because it's been stuffily closed. – Bob Stein Aug 10 '17 at 13:16

Series (like deer, salmon, and sheep) is pronounced and spelled the same in the plural as in the singular. If either the singular or the plural is used as a possessive, an apostrophe is added to show that in print, though there is no pronunciation difference in speech. Thus,

  • The series doesn't converge. (singular)
  • The series don't converge. (plural)
  • This series' limit is unknown. (singular possessive)
  • These series' limits are unknown. (plural possessive)

More examples can be seen here.

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    This is true, but for quite different reasons. Terms of venery—game animals we hunt—are often invariant: elk,deer,bison. In the case of series, we have the phonological suppression of any /ɨz/ inflectional suffix, whether for plural or possessive or both, on all nouns already ending in /iːz/: series, species, Diogenes, Achilles, Archimedes. This is the real law that underlies the unexplained hand-wavy rule about classical possessives, like Achilles’ tendon. Other examples: 1 species is, 2 species are, 1 species’ name is, 2 species’ names are. Completely invariant in pronunciation. – tchrist Feb 23 '12 at 15:46
  • @tchrist Hmm, you say there are two different reasons, but then you don't give a reason for the first case. WHY are names of game animals unchanged in the plural? Do you know? Now that you bring it up, it's an interesting question. – Jay Feb 23 '12 at 17:49
  • Nobody really knows why; and it's not only beasts of venery -- sheep also has a Zero plural, but bear, wolf, and crow don't. And species, series, etc. are all Greek and Latin words, borrowed intact with the Greek and Latin plurals (if any), which are all invariant (Fifth Declension nouns for the most part). – John Lawler Feb 23 '12 at 18:12
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    @JohnLawler It’s not just the adding of an /ɨz/ inflection; it’s that you only ever get one of them no matter whether it’s possessive or plural, so plural possessives still have just one /ɨz/, and that the rare /iːz/ nouns can take zero /ɨz/ inflections, whereas the rest can take one but not two. Historically possessive /ɨz/ was also suppressed in the formulaic for goodness’ sake, for conscience’ sake, for righteousness’ sake. Unrelatedly, remember also the old in speciē and in seriē, which were ablative singulars of speciēs and seriēs. I think specie may still be used for money. – tchrist Feb 23 '12 at 18:36
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    It’s somewhat odd that English kept the 5th-declension’s -s in the singulars for series and species, because the Romance languages did not. There serie (with appropriate diacritics as needed) is singular and series is plural: ES: una serie, unas series FR: une série, des séries. – tchrist Feb 23 '12 at 18:45

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