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I understand that 「の」 can be used to indicate possession or to change a noun
to a modifier for another noun. But neither of those seems to be the case
here.

What usage of 「の」 is being used here?
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2016-04-27T01:37:04.697
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2016-04-27T04:58:11.180
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particle-の
How is 「の」 used in 終わりのない?
終わりのない is not a complete sentence. This phrase can be used as a _relative
clause_ which modifies another noun.

>   * 終わりのない話 a story which has no end; a never-ending story
>   * 終わりがない話 a story which has no end; a never-ending story
>

As you can see, this type of の is a subject marker (just like が) which can be
used only in relative clauses.

See: [How does the の work in
「日本人の知らない日本語」?](https://japanese.stackexchange.com/q/12825/5010)
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2016-04-27T01:48:08.643
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2016-04-27T01:53:42.447
2017-04-13T12:43:44.207
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answer