定Concentration
別境五之第四。專注不散為性，智依為業。
漢zh · Xuanzang 譯
別境五之第四。專注不散為性，智依為業。
經
[共傳] 阿含中定之修行義散見四禪四無量心等章，未有獨立心所定義段；止觀教理與南傳禪修義理高度對應（見巴段 SN 56.1 引文）。
[大乘] 《解深密經》卷三（分別瑜伽品），佛告彌勒菩薩奢摩他定義：
即於如所善思惟法，獨處空閑作意思惟。復即於此能思惟心，內心相續，作意思惟。如是正行多安住故，起身輕安及心輕安，是名奢摩他。
注：奢摩他（śamatha）為定之一種修行方式，與毘鉢舍那（vipaśyanā）並提；定（samādhi）為其更廣義之所依心所，奢摩他為定之特定修法。
論
《成唯識論》卷五：
於所觀境，令心專注不散為性，智依為業。謂觀德、失、俱非境中，由定令心專注不散，依斯便有決擇智生。
按：《成唯識論》附加「謂觀德、失、俱非境中⋯⋯依斯便有決擇智生」——「依斯」= Asg 之 sanniśraya（所依），「決擇智生」= jñāna-jananam（智之生起）。此為 Asg jñāna-sanniśrayadāna 之《成唯識論》版本，點名定所提供之 jñāna 為「決擇智」，並明確標示定慧銜接為《成唯識論》之結構性主張。三語呼應完整：Asg 功能子句 → 《成唯識論》漢語顯化 → SN 56.1 經具體實例（定→知四諦，見巴段）。
梵saṃskṛta
sam-（印歐祖語 *sem-「一、共」；同源 Lat sem-/sim-、Eng same）+ ā-（「向」；介詞前綴）+ √dhā（PIE *dʰeh₁-「置」；同源 Lat con-dō、Eng do, deed）。直譯「合一—向—置」= 「等持／令心合於一境」。
√dhā 同根聯繫：信（śrad-dhā，→#19，「以心置」）與定（sam-ā-dhā，「合一安置」）共此根——別境五心所之 cultivation 鏈在梵文構詞層即已環抱。首於信（heart-placed），終於定（mind-collectedly-placed），兩端皆 √dhā 之派生。Latin con-dō（合置／立、儲）為 sam-ā-dhā 之結構等位詞。√dhā 家族：
| 複合詞 | 構造 | 義 |
|---|---|---|
| śrad-dhā（信，→#19） | 「以心置於彼」 | faith / 被信任 |
| sam-ā-dhā（定，本條 #17） | 「合一安置於境」 | concentration / collectedness |
| vi-dhā | 「分置」 | ordained, disposed |
| ni-dhā | 「下置」→「儲存」 | treasure, deposit |
《阿毘達磨集論》（阿毘達磨-samuccaya，Pradhan 校本，saṃskāra-skandha 心所列定義）：
samādhiḥ katamaḥ / upaparīkṣye vastuni cittasya ekāgratā / jñāna-sanniśrayadāna-karmakaḥ //
何為定？於所觀察境（upaparīkṣya-vastu），心之一境性（cittasya ekāgratā）為性。為智之所依（jñāna-sanniśrayadāna）為業。
功能子句 jñāna-sanniśrayadāna「為智之所依」完成別境五心所之 Asg-internal cultivation 架構——信（→#19）之功能為 chanda-sanniśrayadāna，欲（→#14）之功能為 vīryādāna-sanniśrayadāna，念（→#16）之功能（玄奘顯化）為「定依」，定（本條）之功能為 jñāna-sanniśrayadāna——每一心所之功能子句皆 name 下一心所為其作用之果。samādhi 之功能恰指向次條慧（→#18 prajñā），鏈於此閉合，轉外為慧之「斷疑」。
按：《成唯識論》「令心專注不散」= Asg cittasya ekāgratā（一境性）；《成唯識論》「智依為業」= Asg jñāna-sanniśrayadāna——逐詞對應。Asg 功能子句之「jñāna」所指即《成唯識論》「決擇智」，即南傳 SN 56.1 之「知四諦」——三個表述指同一認知事件。定與慧之關係因此確定：定提供平台，慧執行作業，二者非目的與工具之關係，乃同一修行事件之兩個描述面向（止觀雙運）。
巴pāḷi
別境心所（pakiṇṇaka cetasika）。五根之定根（samādhindriya），五力之定力（samādhibala），七覺支之定覺支（samādhi-sambojjhaṅga），八正道之正定（sammā-samādhi）。
經
《相應部·諦相應》SN 56.1 Samādhi Sutta：
Samādhiṃ, bhikkhave, bhāvetha; samāhito, bhikkhave, bhikkhu yathābhūtaṃ pajānāti. Kiñca yathābhūtaṃ pajānāti? 'Idaṃ dukkha'nti yathābhūtaṃ pajānāti, 'ayaṃ dukkhasamudayo'ti yathābhūtaṃ pajānāti, 'ayaṃ dukkhanirodho'ti yathābhūtaṃ pajānāti, 'ayaṃ dukkhanirodhagāminī paṭipadā'ti yathābhūtaṃ pajānāti.
比丘！修定。得定之比丘如實了知。何所如實了知？如實了知此是苦、此是苦集、此是苦滅、此是趣苦滅道。
按：本經置於諦相應（Sacca-saṃyutta）而非定相應，正示定之價值在使能見四諦——即 Asg「智之所依」之經顯例。SN 56.1 之具體 payload（samādhi → 知四諦）即 Asg jñāna-sanniśrayadāna 之經典實例：jñāna 所指，在經（經）層面，正是苦集滅道之如實知。
論
《清淨道論》XIV.139（行蘊·別境）以四相分析定：
| 四相 | Pāli | 漢譯 |
|---|---|---|
| 相（lakkhaṇa） | avikkhepa / cittassa ekaggatā | 心一境性 |
| 業（rasa） | sahajātānaṃ saṃpiṇḍana | 令俱生諸法集聚 |
| 現（paccupaṭṭhāna） | upasama | 寂靜 |
| 足處（padaṭṭhāna） | sukha | 樂 |
按：Asg cittasya ekāgratā（心一境性）與 Vism cittassa ekaggatā 為同一複合詞之梵巴雙形——citta（心）+ eka（一）+ agra/agga（點）+ -tā/-tā（性）——morpheme 字字對應。此為別境 morphemic 共傳系列之第三例（第一：欲 kartṛ-kāmatā ↔ kattu-kamyatā，→#14；第二：念 asaṃpramoṣa ↔ asammosa，→#16）。Vism 以 sukha（樂）為定之足處，引 AN 11.1「Sukhino cittaṃ samādhiyati」（樂者之心入於定）：定非苦修苦逼之果，乃樂之自然延展。此「樂→定」之情感序列為 Asg 之純分析框架所略，Vism 補之，豐富定之現象學圖像。
漢綜述zh-synthesis
「定」之梵文 samādhi 為三段合成——sam-（印歐祖語 *sem- 「一、共」，同源拉丁 sem-/sim- 與英文 same）+ ā-（向；介詞前綴）+ √dhā（印歐祖語 *dʰeh₁- 「置」，同源拉丁 con-dō 「合置／立、儲」與英文 do, deed）——直譯「合一—向—置」即「等持」「令心合一安置於境」。Pāli samādhi 直承同形。√dhā 為梵文佛教詞匯之核心動詞根之一，派生諸要詞：śrad-dhā（信 →#19，以心置）、sam-ā-dhā（定，本條，合一安置）、vi-dhā（分置，律度）、ni-dhā（下置，儲存）。其中信與定共此 √dhā 根——別境五心所之修習鏈於梵文構詞層即已環抱：首於信（heart-placed），終於定（mind-collectedly-placed），兩端皆 √dhā 之派生。拉丁 con-dō（合置／立、儲）為 sam-ā-dhā 之結構等位詞（con- ≈ sam-；dō ≈ √dhā），亦為英文「foundation」之拉丁源頭——兩語族於同一動詞核心給出「奠基」之共義，可為西方讀者接通梵文 samādhi 之奠基義（非英譯 concentration 所傳之「努力專注」）。
《阿毘達磨集論》之定義簡潔：「samādhiḥ katamaḥ / upaparīkṣye vastuni cittasya ekāgratā / jñāna-sanniśrayadāna-karmakaḥ //」（何為定？於所觀察境，心之一境性為性。為智之所依為業。）玄奘《成唯識論》「於所觀境，令心專注不散為性，智依為業。謂觀德、失、俱非境中，由定令心專注不散，依斯便有決擇智生」乃此梵本之逐字對應——upaparīkṣya-vastu 即「所觀境」、ekāgratā 即「專注不散／一境性」、jñāna-sanniśrayadāna 即「智依為業」；補入「依斯便有決擇智生」一句明示功能子句所指之 jñāna 即「決擇智」。此功能子句閉合Asg 別境心所之內在修習架構——每一心所之功能子句皆指名下一心所為其作用之果：信（→#19）之 chanda-sanniśrayadāna 指向欲（→#14）；欲之 vīryādāna-sanniśrayadāna 指向精進；念（→#16）之功能（玄奘顯化）為「定依」；定（本條）之 jñāna-sanniśrayadāna 指向慧（→#18），鏈於此閉合而轉外為慧之斷疑。換言之：別境五非平行之五心所，乃功能子句層層環扣之分階序列——此架構非後人添加之教學圖示，乃 Asg 在功能子句中之內建設計。
此條於別境五中為梵巴形態對應之第三例（接續欲之 kartṛ-kāmatā ↔ kattu-kamyatā 與念之 asaṃpramoṣa ↔ asammosa）——Asg cittasya ekāgratā（心一境性）與《清淨道論》XIV.139 cittassa ekaggatā 為同一複合詞之梵巴雙形：citta（心）+ eka（一）+ agra/agga（點）+ -tā/-tā（性），字字對應，僅 sandhi 內之送氣音差異。此為別境形態共傳系列之第三例：第一為欲之 kartṛ-kāmatā ↔ kattu-kamyatā（→#14）；第二為念之 asaṃpramoṣa ↔ asammosa（→#16）；第三即定之 ekāgratā ↔ ekaggatā（本條）。三例構成一組——別境五之核心 cetasika 於形態層皆有梵巴雙形之精確對應，morpheme 層之共傳於 51 心所中以此三例為集中見證之一組。Pāli 經典證據密度亦厚——定為三十七道品之多重核心法：五根之定根（samādhindriya）、五力之定力（samādhibala）、七覺支之定覺支（samādhi-sambojjhaṅga）、八正道之正定（sammā-samādhi）。《相應部》SN 56.1《Samādhi Sutta》「Samādhiṃ, bhikkhave, bhāvetha; samāhito, bhikkhave, bhikkhu yathābhūtaṃ pajānāti」（修定，得定者如實了知）所載「了知」之具體內容即四聖諦——而本經安置於諦相應（Sacca-saṃyutta）而非定相應，此置位本身即經典編集之教義表態：定之價值不在定本身之到達，乃在使能見四諦如實——即 Asg「智之所依」之經顯實例。大乘《解深密經》分別瑜伽品之奢摩他（śamatha）定義立後緊隨毘鉢舍那（vipaśyanā）並提，乃止觀雙運架構之大乘表述：定（止）提供平台，慧（→#18，觀）執行作業，二者實為一修行事件之兩面。
《清淨道論》XIV.139 以四相分析定：相為不散、心一境性（avikkhepa / cittassa ekaggatā）；業為令俱生諸法集聚（sahajātānaṃ saṃpiṇḍana）；現為寂靜（upasama）；足處為樂（sukha）。其中「足處為樂」一目具關鍵修持涵義——並非苦修苦逼能成定，乃心已安樂者方能入定：《增支部》AN 11.1 之公式「Sukhino cittaṃ samādhiyati」（樂者之心入於定）顯示巴利傳統對定之發生機制為「樂→定」之自然延展，非「努力→定」之強迫專注。此「樂為足處」之情感序列為 Asg 之純分析框架所略，《清淨道論》補之，使現代讀者於修持中常見之「咬牙專注」誤區得以矯正。然修持之根本仍在定慧不可分——《成唯識論》明言「外道邪定亦是定心所之運作」，定本身通三性，差別不在定之有無，乃在所緣是否如理、引導之慧（→#18）是否如理。定無慧為枯定（單純之止息）；慧無定無立足之地。定慧一體，止觀雙運，已於 Asg 之功能子句層由定指向慧之顯式銜接所內建——此即修持上「定慧雙修」說法之 Sanskrit 文本根。
漢譯三選擇——「三摩地」（samādhi 音譯，保留梵音而漢人讀者隔）、「等持」（依 sam-ā-dhā 構詞之直譯，保留「合一安置」之動性而過於專技）、「定」（玄奘所選，取功能而失構詞）——三者各有得失。本譯保留「定」為通行譯，亦因「定」字漢文已含「安置而不動」之動詞義（《說文》「定，安也」），合 sam-ā-dhā 之核心。但「定」字易令現代讀者誤讀為「靜止之態」（停止）；其實 samādhi 之核心非靜止，乃心於所緣之合一保持——是動態之收攝，非靜態之停滯。英譯之 concentration 為通行譯，但失兩重——既失 sem-/sam-「一、共」之「合一」義（concentrate 之 con- 雖同源 sam- 但語感已被「努力集中」覆蓋），亦失 √dhā 之「置」義；Ñāṇamoli 所譯之 collectedness 較佳，能保留 samādhāna（合置之動作）之收攝義，避開現代英文 concentrating 所暗示之「咬牙努力」誤讀。收尾之關鍵架構觀察：信 śrad-dhā（→#19）與定 sam-ā-dhā（本條）共 √dhā 根——別境五修習鏈之首尾兩環皆「置心」之動詞派生，此非偶然之同根，乃 Asg 設計於梵文構詞層之深層架構：自信之「置心於可信者」始，至定之「置心於所觀者」終，中間欲、念之展開皆「置心」之變奏。漢譯失此構詞層之共鳴（信、定二字無漢字構詞之同源），梵文形態學則為此架構之沉默見證。
定 ——於所觀境，令心專注不散為性，智依為業。
英綜述en-synthesis
Sanskrit samādhi compounds three morphemes: sam- (PIE *sem- "one, together," cognate with Latin sem-/sim- and English same) + ā- (a directional prefix, "toward") + √dhā (PIE *dʰeh₁- "to place," cognate with Latin con-dō "to deposit, found, establish" and English do, deed). The literal compositional sense — together-toward-place — yields one-pointed placing, the gathering of mind onto a single object. Two etymological observations carry doctrinal weight. First, samādhi and śrad-dhā (→#19) share the root √dhā; they are sister formations under the same verbal stem. Śrad-dhā is heart-placed, sam-ā-dhā is evenly-placed. The cultivation chain thus opens on śraddhā (heart-placing) and closes on samādhi (mind-collectedly-placing), with chanda (→#14), adhimokṣa (→#15), and smṛti (→#16) as the intervening links — all bookended in Sanskrit morphology itself. Second, the Latin parallel con-dō — to deposit, store, found — gives a structural English-side analog. The conventional translation "concentration" is functional but loses both connections; Ñāṇamoli prefers "collectedness," capturing samādhāna (the gathering-act) rather than the effortful "concentrating" the modern reader hears.
Samādhi is the fourth of the five object-determining mental factors (viniyata, 別境五) and the most canonically-named factor in the contemplative path: samādhindriya (faculty), samādhibala (power), samādhi-sambojjhaṅga (awakening factor), sammā-samādhi (path-limb). Asaṅga's Abhidharma-samuccaya defines it tersely: upaparīkṣye vastuni cittasya ekāgratā — "with respect to an object being investigated, the mind's one-pointedness" — with function jñāna-sanniśrayadāna-karmaka: providing the basis for jñāna (wisdom). Xuanzang's "於所觀境，令心專注不散為性，智依為業，依斯便有決擇智生" is verbatim and adds an explicit forwarding clause — 依斯便有決擇智生 — that names the specific jñāna the samādhi enables. The function-clause closes the cultivation chain: śraddhā (→#19) → chanda (→#14) → vīrya → smṛti (→#16) → samādhi → prajñā (→#18). Each karman clause names the next factor; samādhi's names jñāna; the chain terminates and turns outward into wisdom's saṃśaya-vyāvartana (doubt-removal, cf. →#18).
The morphemic identity. Across separate transmission lines, cittasya ekāgratā (Asg, Sanskrit) and cittassa ekaggatā (Visuddhimagga XIV.139, Pāli) are the same compound, morpheme for morpheme. The match joins two earlier viniyata parallels — kartṛ-kāmatā ↔ kattu-kamyatā (chanda, →#14) and asaṃpramoṣa ↔ asammosa (smṛti, →#16) — completing a triad of cross-tradition morphemic matches in this cluster. Visuddhimagga gives the four-fold: characteristic avikkhepa / cittassa ekaggatā; function sahajātānaṃ saṃpiṇḍana (the gathering of co-arising states); manifestation upasama (peace); proximate cause sukha (bliss). The fourth point — sukha as padaṭṭhāna — is doctrinally important and absent from Asaṅga: the Pāli tradition holds that samādhi arises naturally from bliss (sukhino cittaṃ samādhiyati, AN 11.1), not from forced concentration. The modern image of samādhi as effortful focus reads against the canonical claim that the mind which is already at ease is the mind that gathers.
Saṃyutta Nikāya 56.1's placement in the Truth-Connected Discourses (Sacca-saṃyutta) rather than in the Samādhi Saṃyutta is itself the doctrine: samādhi's value is not as a state to be reached but as the mental condition under which the four truths can be seen as they are. This precisely mirrors Asaṅga's jñāna-sanniśrayadāna. The Saṃdhinirmocana-sūtra's definition of śamatha (奢摩他) as the concentrated mind applied to "a well-reflected-upon object" — followed immediately by the pairing with vipaśyanā — gives the Mahāyāna articulation of the same structural claim: samādhi (止) provides the stable platform; prajñā (→#18, 觀) executes the discerning work. The pair is one practice — 止觀雙運 — already encoded at Asaṅga's function-clause level by the explicit handoff from samādhi to jñāna.
Samādhi is morally neutral — non-Buddhist contemplatives also develop it; Cheng Weishi Lun notes that even 外道邪定 is a functioning of the samādhi cetasika. What distinguishes wholesome from unwholesome samādhi is not the factor itself but what is held and what guidance attends the holding. Samādhi without prajñā (→#18) is mere stilling; prajñā without samādhi has no stable platform. And samādhi without smṛti (→#16) has nothing reliably to hold: the object drifts. The four in sequence — chanda (→#14) generates the reach; adhimokṣa (→#15) seals the verdict; smṛti holds the sealed object; samādhi deepens the hold — constitute the functional spine of the 別境 cultivation chain, with prajñā (→#18) as its outward-acting termination.
Concentration — with respect to an object being investigated, the mind's one-pointedness: this is its nature. To provide the basis upon which wisdom takes hold and the deciding-knowing arises: this is its function.
譯translator's note
譯者按： 定為一切部派共許之別境心所，亦三十七道品核心法：定根、定力、定覺支、正定。定通三性——外道邪定亦是定心所之運作，差別在所緣與引導之慧（→#18）是否如理。定之價值不在定本身，在「智依為業」——定是慧之基礎，非目的；信（→#19）為 √dhā 家族之首，定（本條）為 √dhā 家族之尾，別境五修習鏈首尾呼應，梵文構詞層即是此架構之沉默見證。