δεῖ (dei): all forms
δεῖ means “it is necessary, one must”. Below is its full conjugation in Ancient Greek.
Present active
Present active | Indicative | Subjunctive | Optative | Imperative |
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| 1st singular | δέω | δέω | δέοιμι | |
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| 2nd singular | δέεις | δέῃς | δέοις | δέε |
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| 3rd singular | δέει | δέῃ · δῇ | δέοι | δεέτω |
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| 1st plural | δέομεν | δέωμεν | δέοιμεν | |
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| 2nd plural | δέετε | δέητε | δέοιτε | δέετε |
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| 3rd plural | δέουσι(ν) | δέωσι(ν) | δέοιεν | δεόντων · δεέτωσαν |
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Imperfect active
Imperfect active | Indicative |
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| 1st singular | ἔδεον |
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| 2nd singular | ἔδεες |
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| 3rd singular | ἔδει · ἔδεε |
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| 1st plural | ἐδέομεν |
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| 2nd plural | ἐδέετε |
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| 3rd plural | ἔδεον |
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Future active
Future active | Indicative | Optative |
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| 3rd singular | δεήσει | δεήσοι |
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Aorist active
Aorist active | Indicative | Subjunctive | Optative | Imperative |
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| 3rd singular | ἐδέησε(ν) | δεήσῃ | δεήσαι · δεήσειε · δεήσειεν | δεησάτω |
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Infinitives
Infinitives | Active |
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| Present | δεῖν |
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| Future | δεήσειν |
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| Aorist | δεῆσαι |
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Participles
Present active participle, singular | Masculine | Feminine | Neuter |
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| Nominative | δέων | δέουσα | δέον |
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| Genitive | δέοντος | δεούσης | δέοντος |
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| Dative | δέοντι | δεούσῃ | δέοντι |
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| Accusative | δέοντα | δέουσαν | δέον |
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| Vocative | δέον | δέουσα | δέον |
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Present active participle, plural | Masculine | Feminine | Neuter |
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| Nominative | δέοντες | δέουσαι | δέοντα |
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| Genitive | δεόντων | δεουσῶν | δεόντων |
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| Dative | δέουσι(ν) | δεούσαις | δέουσι(ν) |
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| Accusative | δέοντας | δεούσας | δέοντα |
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| Vocative | δέοντες | δέουσαι | δέοντα |
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Present participle | Neuter |
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| Nominative | δεῖν |
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| Accusative | δεῖν |
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| Vocative | δεῖν |
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Meaning and examples of δεῖ
Source: Socratos (socratos.org), a free reader for Ancient Greek and Latin. Grammar from the Perseus Treebank and Morpheus; dictionary entries from Liddell-Scott-Jones, A Greek-English Lexicon (Perseus Digital Library, CC BY-SA). Counts are from the texts on Socratos.