**ده‌دهی متناوب** یا **اعشاری متناوب** (انگلیسی: Repeating decimal) نوعی نمایش ده‌دهی است که ارقامش تابع متناوب هستند (به این معنی که در بازه‌های منظم تکرار می‌شوند) و بخشی که تا بی‌نهایت تکرار می‌شود صفر نیست. می‌توان ثابت کرد که یک عدد عدد گویا است اگر و فقط اگر نمایش ده‌دهی آن یا متناوب باشد یا مختوم.
اگر در شکل کسری یک عدد در مخرج کسر پس از تجزیه کردن به عامل‌های اول ، عامل‌های ۲ و ۵ وجود نداشته باشد. چنانچه صورت را به مخرج تقسیم کنیم به باقیمانده صفر نخواهیم رسید و خارج قسمت حقیقی بدست نمی‌آید، بلکه در خارج قسمت بعد از ممیز رقم یا ارقام مرتب تکرار می‌شوند. این نمایش را نمایش **ده‌دهی متناوب ساده** می‌نامند.
چنانچه کسر پس از تجزیه کردن به عامل‌های اول عامل‌های ۲و ۵ و سایر عوامل اول وجود داشته باشد در این صورت خارج قسمت بعد از ممیز غیر از ارقام دوره گردش ارقام دیگری قبل از دوره گردش وجود دارد که تکراری نمی‌شوند و باقیمانده هرگز صفر نخواهد شد. این عدد را عدد **ده‌دهی متناوب مرکب** می‌نامند.

جستارهای وابسته
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* نمایش ده‌دهی

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طبقه‌بندی اعداد| مختلط {\displaystyle :\;\mathbb {C} } | 

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| حقیقی {\displaystyle :\;\mathbb {R} } | 

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| گویا {\displaystyle :\;\mathbb {Q} } | 

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| صحیح {\displaystyle :\;\mathbb {Z} } | 

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| حسابی  | 

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| طبیعی {\displaystyle :\;\mathbb {N} } | 

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| یک: 1 |
| اعداد اول |
| اعداد مرکب |

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| صفر: 0 |

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| اعداد صحیح منفی |

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| کسری | 

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| مختوم |
| متناوب | 

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| ساده |
| مرکب |

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| گنگ | 

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| اعداد گنگ جبری |
| متعالی |

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| موهومی |

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منابع
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* مشارکت‌کنندگان ویکی‌پدیا. «Repeating decimal». در *دانشنامهٔ ویکی‌پدیای انگلیسی*، بازبینی‌شده در ۴ فوریه ۲۰۱۹.