NihontoWatch Mon

NihontoWatch

マーケット
事典
鑑定
NihontoWatch Mon

NihontoWatch

マーケット
事典
鑑定

説明

Antique Japanese Sword Wakizashi Signed by Kunihide with NBTHK Hozon Certificate 【Description】 Summary This blade was signed by Kawachi no Kami Minamoto Kunihide (河内守源国英), who was active during the Enpo era (1673-1681:Early Edo period). Kawachi no Kami is an honorable official title given by the imperial court for his excellent craftsmanship. Minamoto is his surname he used as his maker’s name. In his career, he served the Izumo domain (Today’s Shimane prefecture). Izumo is the most famous place for producing Tamahagane, special carbon steel used to make Japanese swords. We assume Yoshiyuki had easy access to refined, high-quality steel because of where he lived. We are confident you can appreciate Yoshiyuki’s superb craftsmanship in this blade. Since this blade was registered in Shimane prefecture, we believe a few of the previous owners lived in Shimane prefecture for many years and this Wakizashi was passed down for many generations. What is Wakizashi? WAKIZASHI refers to a 30-60 cm long blade (11.8-28.6 inches) and was worn on the waist along with UCHI-GATANA (Katana). Samurai carried WAKIZASHI as a backup sword next to Katana. Samurai needed to use Wakizashi when he fought in a small room or with proximity where Katana would be too long to unsheathe. Also, when Samurai entered a castle, he had to leave his Katana to the castle guard. In contrast, Wakizashi was allowed to bring inside as self-protection. The use of Wakizashi became more widespread among Samurais during the Edo period. (1603-1868 A.D. ) Because the Edo Government had launched the national law to force all Samurais to wear two Japanese swords (Katana and Wakizashi) to identify themselves as the regime’s military officers. This blade is appraised as a Hozon Token (保存刀剣) issued by NBTHK (Nihon Bijutsu Touken Hozon Kyokai:日本美術刀剣保存協会). This authentication paper was only given to authentic Japanese swords, well preserved with artistic value. *Please keep in mind that there is a tiny black rust spot near the tip of the blade. If you like to see the detailed condition, please feel free to contact us. 【 Blade】 Cutting Edge Length(Nagasa) : 40.7 cm (16.0 inches) Curvature(Sori) : 0.8 cm (0.31 inches) Hamon: The crystalline structure which forms along the cutting edge of a blade as a result of the hardening process Jimon(Jihada): visible steel surface pattern created by folding and hammering during forging process Kissaki : Kissaki is the tip of the Japanese sword. Nakago : Nakago is the tang of the Japanese sword. Japanese swordsmiths left the black rust on the tang on purpose to prevent red rust while the tang is in its handle. And the discoloration of the tang was created over time, which is a great indicator for a Japanese sword specialist to estimate when the sword was forged. Koshirae: Koshirae is the mounting of the Japanese sword. There are several parts that consist of Koshirae such as Saya(Scabbard), Tsuka( Handle), Tsuba(Handguard). Fuchi-Kashira : A pair of matching sword fittings that cover the upper and bottom parts of its sword hilt. Its surface is Nanakoji (魚子地). This process makes a uniform minimal protrusions pattern by hitting the Nanako-Ji Tagane (魚子地鏨, a chisel for this technique) on a metal surface. This decorative technique is often seen on sword mountings. We assume Karakusa pattern (Ivy) is the theme of this design. It is a pattern in which stems and leaves of vines are twined and make curves. Since ivy has a strong vitality and grows up without interruption, people regarded this design as a symbol of prosperity and longevity. Vine is called Tsuru (蔓) in Japanese, and it has another pronunciation; “Man.” There is a word 万 (it is also read Man), which means ten thousand. In the Karakusa pattern, leaves and vines are connected like Obi (帯, belt). The word “帯” can also be read “Tai.” Due to its pronunciation, the term “代 (Tai)” is associated. From this word-association game, an idiom 万代 is associated, and it means a thousand generations. In oth

NihontoWatch MonNihontoWatch
MarketEncyclopediaKantei
刀剣›國英›Antique Japanese Sword Wakizashi Signed by Minamoto Kunihide NBTHK Hozon Certificate
脇差保存
國英

Antique Japanese Sword Wakizashi Signed by Minamoto Kunihide NBTHK Hozon Certificate

在銘 · 江戸 · 長さ 40.7cm · 反り 0.8cm

売却済
國英 — 1 of 23
國英 — 2 of 23
國英 — 3 of 23
國英 — 4 of 23
國英 — 5 of 23
國英 — 6 of 23
國英 — 7 of 23
國英 — 8 of 23
國英 — 9 of 23
國英 — 10 of 23
國英 — 11 of 23
國英 — 12 of 23
國英 — 13 of 23
國英 — 14 of 23
國英 — 15 of 23
國英 — 16 of 23
國英 — 17 of 23
國英 — 18 of 23
國英 — 19 of 23
國英 — 20 of 23
國英 — 21 of 23
國英 — 22 of 23
國英 — 23 of 23
1 / 23
1 / 23
國英 — 1 of 23國英 — 2 of 23國英 — 3 of 23國英 — 4 of 23國英 — 5 of 23國英 — 6 of 23國英 — 7 of 23國英 — 8 of 23國英 — 9 of 23國英 — 10 of 23國英 — 11 of 23國英 — 12 of 23國英 — 13 of 23國英 — 14 of 23國英 — 15 of 23國英 — 16 of 23國英 — 17 of 23國英 — 18 of 23國英 — 19 of 23國英 — 20 of 23國英 — 21 of 23國英 — 22 of 23國英 — 23 of 23
法量・詳細
刀工
國英
種別
脇差
活動期
1661–1681年頃(Kanbun-Enpo)
国
出雲
銘
在銘
法量
長さ 40.7cm反り 0.8cm
説明

Antique Japanese Sword Wakizashi Signed by Kunihide with NBTHK Hozon Certificate 【Description】 Summary This blade was signed by Kawachi no Kami Minamoto Kunihide (河内守源国英), who was active during the Enpo era (1673-1681:Early Edo period). Kawachi no Kami is an honorable official title given by the imperial court for his excellent craftsmanship. Minamoto is his surname he used as his maker’s name. In his career, he served the Izumo domain (Today’s Shimane prefecture). Izumo is the most famous place for producing Tamahagane, special carbon steel used to make Japanese swords. We assume Yoshiyuki had easy access to refined, high-quality steel because of where he lived. We are confident you can appreciate Yoshiyuki’s superb craftsmanship in this blade. Since this blade was registered in Shimane prefecture, we believe a few of the previous owners lived in Shimane prefecture for many years and this Wakizashi was passed down for many generations. What is Wakizashi? WAKIZASHI refers to a 30-60 cm long blade (11.8-28.6 inches) and was worn on the waist along with UCHI-GATANA (Katana). Samurai carried WAKIZASHI as a backup sword next to Katana. Samurai needed to use Wakizashi when he fought in a small room or with proximity where Katana would be too long to unsheathe. Also, when Samurai entered a castle, he had to leave his Katana to the castle guard. In contrast, Wakizashi was allowed to bring inside as self-protection. The use of Wakizashi became more widespread among Samurais during the Edo period. (1603-1868 A.D. ) Because the Edo Government had launched the national law to force all Samurais to wear two Japanese swords (Katana and Wakizashi) to identify themselves as the regime’s military officers. This blade is appraised as a Hozon Token (保存刀剣) issued by NBTHK (Nihon Bijutsu Touken Hozon Kyokai:日本美術刀剣保存協会). This authentication paper was only given to authentic Japanese swords, well preserved with artistic value. *Please keep in mind that there is a tiny black rust spot near the tip of the blade. If you like to see the detailed condition, please feel free to contact us. 【 Blade】 Cutting Edge Length(Nagasa) : 40.7 cm (16.0 inches) Curvature(Sori) : 0.8 cm (0.31 inches) Hamon: The crystalline structure which forms along the cutting edge of a blade as a result of the hardening process Jimon(Jihada): visible steel surface pattern created by folding and hammering during forging process Kissaki : Kissaki is the tip of the Japanese sword. Nakago : Nakago is the tang of the Japanese sword. Japanese swordsmiths left the black rust on the tang on purpose to prevent red rust while the tang is in its handle. And the discoloration of the tang was created over time, which is a great indicator for a Japanese sword specialist to estimate when the sword was forged. Koshirae: Koshirae is the mounting of the Japanese sword. There are several parts that consist of Koshirae such as Saya(Scabbard), Tsuka( Handle), Tsuba(Handguard). Fuchi-Kashira : A pair of matching sword fittings that cover the upper and bottom parts of its sword hilt. Its surface is Nanakoji (魚子地). This process makes a uniform minimal protrusions pattern by hitting the Nanako-Ji Tagane (魚子地鏨, a chisel for this technique) on a metal surface. This decorative technique is often seen on sword mountings. We assume Karakusa pattern (Ivy) is the theme of this design. It is a pattern in which stems and leaves of vines are twined and make curves. Since ivy has a strong vitality and grows up without interruption, people regarded this design as a symbol of prosperity and longevity. Vine is called Tsuru (蔓) in Japanese, and it has another pronunciation; “Man.” There is a word 万 (it is also read Man), which means ten thousand. In the Karakusa pattern, leaves and vines are connected like Obi (帯, belt). The word “帯” can also be read “Tai.” Due to its pronunciation, the term “代 (Tai)” is associated. From this word-association game, an idiom 万代 is associated, and it means a thousand generations. In oth

作者について

國英

出雲 · 1661-1681頃

現在3点販売中

›
國英の作 3点が現在販売中→
國英 — 詳細

歴史的背景

江戸は刀の目利きの時代である。本阿弥の鑑定、1719年の享保名物帳、盛んな刀剣書が、戦で抜かれることのなくなった刀を学問の対象へと変えていった。

江戸時代 →

NBTHK鑑定書
Hozon Tōken保存刀剣
Sword Worthy of Preservation
›

銘が正しい、または無銘でも年代・国・系統を確実に指摘できる、保存に値する真正の作と鑑定されたものです。

NBTHKについて›

日本美術刀剣保存協会(NBTHK)は、1948年に設立され、文化庁の監督を受ける公益財団法人で、東京・刀剣博物館に本部を置きます。専門の審査員が出品作を直接審査し、美術的・歴史的価値に応じた鑑定書を発行します。NBTHKの鑑定書は、日本刀および刀装具の真正性を示す最も広く認知された基準です。

NBTHK公式サイト→
販売店
サ
サムライミュージアム
🇯🇵日本から発送
›
✓認証販売店samuraimuseum.jp
✓海外発送可✓英語対応PayPalクレジットカード
返品ポリシー

Returns/exchanges limited to defects caused by shipping (except willful misconduct or gross negligence by the company); customers must contact within 72 hours of receiving the product.

サムライミュージアムの出品一覧を見る→販売店サイトでこの商品を見る→

國英の他の作

すべて見る →
Toyuukai
特別保存
Katana - Tokuho - by Kunihide - 刀 大和守国英(伊勢守国輝前銘) 特別保存刀剣鑑定書付 品番:KA018Katana - Tokuho - by Kunihide - 刀 大和守国英(伊勢守国輝前銘) 特別保存刀剣鑑定書付 品番:KA018

刀

作國英
江戸
¥1,500,000
中野古銭
保存
Katana - Hozon - by Kunihide - B4194 118万円 国英Katana - Hozon - by Kunihide - B4194 118万円 国英

刀

作國英
69.2cm·江戸
¥1,180,000
サムライミュージアム
保存
Tanto - Hozon - by Kunihide - Antique Japanese Sword Tanto Signed by Minamoto Kunihide NBTHK Hozon CertificateTanto - Hozon - by Kunihide - Antique Japanese Sword Tanto Signed by Minamoto Kunihide NBTHK Hozon Certificate

短刀

作國英
28.8cm·Kanbun-Enpo (1661-1681)
¥3,458

國英の売約済み

葵美術
Wakizashi - by Kunihide - 無題Wakizashi - by Kunihide - 無題
売切れ

脇差

作國英
33.7cm·新刀
売却済

刀剣

  • 刀
  • 脇差
  • 短刀
  • 太刀
  • 薙刀
  • 槍

刀装具

  • 鍔
  • 縁頭
  • 小柄
  • 目貫

甲冑武具

  • 兜
  • 甲冑

鑑定別

  • 特重
  • 重要
  • 特別保存
  • 保存

リソース

  • 刀剣商一覧
  • 刀工一覧
  • 誌上鑑定
  • すべて見る
Nihontowatch© 2026
利用規約プライバシーCookie運営者情報

説明

Antique Japanese Sword Wakizashi Signed by Kunihide with NBTHK Hozon Certificate 【Description】 Summary This blade was signed by Kawachi no Kami Minamoto Kunihide (河内守源国英), who was active during the Enpo era (1673-1681:Early Edo period). Kawachi no Kami is an honorable official title given by the imperial court for his excellent craftsmanship. Minamoto is his surname he used as his maker’s name. In his career, he served the Izumo domain (Today’s Shimane prefecture). Izumo is the most famous place for producing Tamahagane, special carbon steel used to make Japanese swords. We assume Yoshiyuki had easy access to refined, high-quality steel because of where he lived. We are confident you can appreciate Yoshiyuki’s superb craftsmanship in this blade. Since this blade was registered in Shimane prefecture, we believe a few of the previous owners lived in Shimane prefecture for many years and this Wakizashi was passed down for many generations. What is Wakizashi? WAKIZASHI refers to a 30-60 cm long blade (11.8-28.6 inches) and was worn on the waist along with UCHI-GATANA (Katana). Samurai carried WAKIZASHI as a backup sword next to Katana. Samurai needed to use Wakizashi when he fought in a small room or with proximity where Katana would be too long to unsheathe. Also, when Samurai entered a castle, he had to leave his Katana to the castle guard. In contrast, Wakizashi was allowed to bring inside as self-protection. The use of Wakizashi became more widespread among Samurais during the Edo period. (1603-1868 A.D. ) Because the Edo Government had launched the national law to force all Samurais to wear two Japanese swords (Katana and Wakizashi) to identify themselves as the regime’s military officers. This blade is appraised as a Hozon Token (保存刀剣) issued by NBTHK (Nihon Bijutsu Touken Hozon Kyokai:日本美術刀剣保存協会). This authentication paper was only given to authentic Japanese swords, well preserved with artistic value. *Please keep in mind that there is a tiny black rust spot near the tip of the blade. If you like to see the detailed condition, please feel free to contact us. 【 Blade】 Cutting Edge Length(Nagasa) : 40.7 cm (16.0 inches) Curvature(Sori) : 0.8 cm (0.31 inches) Hamon: The crystalline structure which forms along the cutting edge of a blade as a result of the hardening process Jimon(Jihada): visible steel surface pattern created by folding and hammering during forging process Kissaki : Kissaki is the tip of the Japanese sword. Nakago : Nakago is the tang of the Japanese sword. Japanese swordsmiths left the black rust on the tang on purpose to prevent red rust while the tang is in its handle. And the discoloration of the tang was created over time, which is a great indicator for a Japanese sword specialist to estimate when the sword was forged. Koshirae: Koshirae is the mounting of the Japanese sword. There are several parts that consist of Koshirae such as Saya(Scabbard), Tsuka( Handle), Tsuba(Handguard). Fuchi-Kashira : A pair of matching sword fittings that cover the upper and bottom parts of its sword hilt. Its surface is Nanakoji (魚子地). This process makes a uniform minimal protrusions pattern by hitting the Nanako-Ji Tagane (魚子地鏨, a chisel for this technique) on a metal surface. This decorative technique is often seen on sword mountings. We assume Karakusa pattern (Ivy) is the theme of this design. It is a pattern in which stems and leaves of vines are twined and make curves. Since ivy has a strong vitality and grows up without interruption, people regarded this design as a symbol of prosperity and longevity. Vine is called Tsuru (蔓) in Japanese, and it has another pronunciation; “Man.” There is a word 万 (it is also read Man), which means ten thousand. In the Karakusa pattern, leaves and vines are connected like Obi (帯, belt). The word “帯” can also be read “Tai.” Due to its pronunciation, the term “代 (Tai)” is associated. From this word-association game, an idiom 万代 is associated, and it means a thousand generations. In oth

NihontoWatch MonNihontoWatch
MarketEncyclopediaKantei
刀剣›國英›Antique Japanese Sword Wakizashi Signed by Minamoto Kunihide NBTHK Hozon Certificate
脇差保存
國英

Antique Japanese Sword Wakizashi Signed by Minamoto Kunihide NBTHK Hozon Certificate

在銘 · 江戸 · 長さ 40.7cm · 反り 0.8cm

売却済
國英 — 1 of 23
國英 — 2 of 23
國英 — 3 of 23
國英 — 4 of 23
國英 — 5 of 23
國英 — 6 of 23
國英 — 7 of 23
國英 — 8 of 23
國英 — 9 of 23
國英 — 10 of 23
國英 — 11 of 23
國英 — 12 of 23
國英 — 13 of 23
國英 — 14 of 23
國英 — 15 of 23
國英 — 16 of 23
國英 — 17 of 23
國英 — 18 of 23
國英 — 19 of 23
國英 — 20 of 23
國英 — 21 of 23
國英 — 22 of 23
國英 — 23 of 23
1 / 23
1 / 23
國英 — 1 of 23國英 — 2 of 23國英 — 3 of 23國英 — 4 of 23國英 — 5 of 23國英 — 6 of 23國英 — 7 of 23國英 — 8 of 23國英 — 9 of 23國英 — 10 of 23國英 — 11 of 23國英 — 12 of 23國英 — 13 of 23國英 — 14 of 23國英 — 15 of 23國英 — 16 of 23國英 — 17 of 23國英 — 18 of 23國英 — 19 of 23國英 — 20 of 23國英 — 21 of 23國英 — 22 of 23國英 — 23 of 23
法量・詳細
刀工
國英
種別
脇差
活動期
1661–1681年頃(Kanbun-Enpo)
国
出雲
銘
在銘
法量
長さ 40.7cm反り 0.8cm
説明

Antique Japanese Sword Wakizashi Signed by Kunihide with NBTHK Hozon Certificate 【Description】 Summary This blade was signed by Kawachi no Kami Minamoto Kunihide (河内守源国英), who was active during the Enpo era (1673-1681:Early Edo period). Kawachi no Kami is an honorable official title given by the imperial court for his excellent craftsmanship. Minamoto is his surname he used as his maker’s name. In his career, he served the Izumo domain (Today’s Shimane prefecture). Izumo is the most famous place for producing Tamahagane, special carbon steel used to make Japanese swords. We assume Yoshiyuki had easy access to refined, high-quality steel because of where he lived. We are confident you can appreciate Yoshiyuki’s superb craftsmanship in this blade. Since this blade was registered in Shimane prefecture, we believe a few of the previous owners lived in Shimane prefecture for many years and this Wakizashi was passed down for many generations. What is Wakizashi? WAKIZASHI refers to a 30-60 cm long blade (11.8-28.6 inches) and was worn on the waist along with UCHI-GATANA (Katana). Samurai carried WAKIZASHI as a backup sword next to Katana. Samurai needed to use Wakizashi when he fought in a small room or with proximity where Katana would be too long to unsheathe. Also, when Samurai entered a castle, he had to leave his Katana to the castle guard. In contrast, Wakizashi was allowed to bring inside as self-protection. The use of Wakizashi became more widespread among Samurais during the Edo period. (1603-1868 A.D. ) Because the Edo Government had launched the national law to force all Samurais to wear two Japanese swords (Katana and Wakizashi) to identify themselves as the regime’s military officers. This blade is appraised as a Hozon Token (保存刀剣) issued by NBTHK (Nihon Bijutsu Touken Hozon Kyokai:日本美術刀剣保存協会). This authentication paper was only given to authentic Japanese swords, well preserved with artistic value. *Please keep in mind that there is a tiny black rust spot near the tip of the blade. If you like to see the detailed condition, please feel free to contact us. 【 Blade】 Cutting Edge Length(Nagasa) : 40.7 cm (16.0 inches) Curvature(Sori) : 0.8 cm (0.31 inches) Hamon: The crystalline structure which forms along the cutting edge of a blade as a result of the hardening process Jimon(Jihada): visible steel surface pattern created by folding and hammering during forging process Kissaki : Kissaki is the tip of the Japanese sword. Nakago : Nakago is the tang of the Japanese sword. Japanese swordsmiths left the black rust on the tang on purpose to prevent red rust while the tang is in its handle. And the discoloration of the tang was created over time, which is a great indicator for a Japanese sword specialist to estimate when the sword was forged. Koshirae: Koshirae is the mounting of the Japanese sword. There are several parts that consist of Koshirae such as Saya(Scabbard), Tsuka( Handle), Tsuba(Handguard). Fuchi-Kashira : A pair of matching sword fittings that cover the upper and bottom parts of its sword hilt. Its surface is Nanakoji (魚子地). This process makes a uniform minimal protrusions pattern by hitting the Nanako-Ji Tagane (魚子地鏨, a chisel for this technique) on a metal surface. This decorative technique is often seen on sword mountings. We assume Karakusa pattern (Ivy) is the theme of this design. It is a pattern in which stems and leaves of vines are twined and make curves. Since ivy has a strong vitality and grows up without interruption, people regarded this design as a symbol of prosperity and longevity. Vine is called Tsuru (蔓) in Japanese, and it has another pronunciation; “Man.” There is a word 万 (it is also read Man), which means ten thousand. In the Karakusa pattern, leaves and vines are connected like Obi (帯, belt). The word “帯” can also be read “Tai.” Due to its pronunciation, the term “代 (Tai)” is associated. From this word-association game, an idiom 万代 is associated, and it means a thousand generations. In oth

作者について

國英

出雲 · 1661-1681頃

現在3点販売中

›
國英の作 3点が現在販売中→
國英 — 詳細

歴史的背景

江戸は刀の目利きの時代である。本阿弥の鑑定、1719年の享保名物帳、盛んな刀剣書が、戦で抜かれることのなくなった刀を学問の対象へと変えていった。

江戸時代 →

NBTHK鑑定書
Hozon Tōken保存刀剣
Sword Worthy of Preservation
›

銘が正しい、または無銘でも年代・国・系統を確実に指摘できる、保存に値する真正の作と鑑定されたものです。

NBTHKについて›

日本美術刀剣保存協会(NBTHK)は、1948年に設立され、文化庁の監督を受ける公益財団法人で、東京・刀剣博物館に本部を置きます。専門の審査員が出品作を直接審査し、美術的・歴史的価値に応じた鑑定書を発行します。NBTHKの鑑定書は、日本刀および刀装具の真正性を示す最も広く認知された基準です。

NBTHK公式サイト→
販売店
サ
サムライミュージアム
🇯🇵日本から発送
›
✓認証販売店samuraimuseum.jp
✓海外発送可✓英語対応PayPalクレジットカード
返品ポリシー

Returns/exchanges limited to defects caused by shipping (except willful misconduct or gross negligence by the company); customers must contact within 72 hours of receiving the product.

サムライミュージアムの出品一覧を見る→販売店サイトでこの商品を見る→

國英の他の作

すべて見る →
Toyuukai
特別保存
Katana - Tokuho - by Kunihide - 刀 大和守国英(伊勢守国輝前銘) 特別保存刀剣鑑定書付 品番:KA018Katana - Tokuho - by Kunihide - 刀 大和守国英(伊勢守国輝前銘) 特別保存刀剣鑑定書付 品番:KA018

刀

作國英
江戸
¥1,500,000
中野古銭
保存
Katana - Hozon - by Kunihide - B4194 118万円 国英Katana - Hozon - by Kunihide - B4194 118万円 国英

刀

作國英
69.2cm·江戸
¥1,180,000
サムライミュージアム
保存
Tanto - Hozon - by Kunihide - Antique Japanese Sword Tanto Signed by Minamoto Kunihide NBTHK Hozon CertificateTanto - Hozon - by Kunihide - Antique Japanese Sword Tanto Signed by Minamoto Kunihide NBTHK Hozon Certificate

短刀

作國英
28.8cm·Kanbun-Enpo (1661-1681)
¥3,458

國英の売約済み

葵美術
Wakizashi - by Kunihide - 無題Wakizashi - by Kunihide - 無題
売切れ

脇差

作國英
33.7cm·新刀
売却済

刀剣

  • 刀
  • 脇差
  • 短刀
  • 太刀
  • 薙刀
  • 槍

刀装具

  • 鍔
  • 縁頭
  • 小柄
  • 目貫

甲冑武具

  • 兜
  • 甲冑

鑑定別

  • 特重
  • 重要
  • 特別保存
  • 保存

リソース

  • 刀剣商一覧
  • 刀工一覧
  • 誌上鑑定
  • すべて見る
Nihontowatch© 2026
利用規約プライバシーCookie運営者情報
NihontoWatch Mon

NihontoWatch

マーケット
事典
鑑定
NihontoWatch Mon

NihontoWatch

マーケット
事典
鑑定