Deponent verb

In linguistics, a deponent verb is a verb that is active in meaning but takes its form from a different voice, most commonly the middle or passive. A deponent verb has no active forms.
Languages with deponent verbs.
"This list may not be exhaustive."
Ancient Greek.
Ancient Greek has middle-voice deponents (some of which are very common) and some passive-voice deponents. An example in classical Greek is (, 'I come' or 'I go'), middle/passive in form but active in translation.
Some 'active' verbs will take middle-form futures, such as how (, 'I hear') becomes (, 'I will hear'), rather than the regular adding of a sigma (like (, 'I stop') becoming (, 'I will stop')). These are still active in translation. For these verbs, there is no future middle, but the future passive is unaffected.
Koine Greek has a few verbs which have very different meanings in the active and middle/passive forms. For example, () means "I set fire to", whereas its middle form () means "I touch". Because is much more common in usage, beginners often learn this form first and are tempted to assume that it is a deponent.
Latin.
Latin has passive-voice deponents, such as "hortārī" ('to exhort'), "verērī" ('to fear'), "loquī" ('to speak'), "blandīrī" ('to flatter'), and many more. (Deponent verbs are passive in form and active in meaning.) The forms regularly follow those of the passive of normal verbs:
Deponents have all the participles normal verbs do, although those of the perfect carry an active meaning, rather than a passive meaning as in the case of normal verbs. Some deponent verbs, such as "sequī" (to follow), use the corresponding forms of other verbs to express a genuine passive meaning. They do not have their own passive forms, nor is it possible to resurrect the "active" forms of the deponent verbs to use for the passive voice (like attempting to use *"hortō" for "I am exhorted").
Additionally, four Latin verbs ("audēre", to dare; "gaudēre", to rejoice; "solēre", to be accustomed; and "fīdere", to trust) are called "semi-deponent", because though they look passive in their perfect forms, they are semantically active in all forms.
Conversely, Latin also has some verbs that are active in form but passive in meaning. "fit" (it is made, done) was used as the passive of "facit" (to do, to make). In the perfect forms (perfect, pluperfect, and future perfect), this was a compound verb just like the passive voice of regular verbs ("factum est", it has been done).
Sanskrit.
Sanskrit has active, middle and passive voices. As the passive is a secondary formation (based on a different stem with middle endings), all deponent verbs take middle-voice forms, such as सच॑ते sác-ate.
Traditional grammar distinguishes three classes of verbs: ‘parasmaipadinaḥ’ (having active forms only), ‘ātmanepadinaḥ’ (having middle forms only) and ‘ubhayapadinaḥ’ (having both forms). Thus, ‘ātmanepadī’ (plural ātmanepadinaḥ) might be considered a deponent verb.
Swedish.
Swedish has a few passive-voice deponents, although its closely related neighbour languages Danish and Norwegian mostly use active corresponding forms. Indeed, Norwegian shows the opposite trend: like in English, active verbs are sometimes used with a passive or middle sense, such as in "boka solgte 1000 eksemplarer" ("the book sold 1000 copies"). -s is the normal passive ending in the Scandinavian languages. 
Norwegian.
Norwegian has several common deponents which use the '-es' passive ending in the active voice, instead of the usual '-er' active ending (and retains the '-es' in the infinitive, where most verbs end solely in '-e'): 
The past tense is indicated by 'd or 't', e.g. "kjentes", "lyktes", "syntes", "trivdes".
Danish.
Modern Danish, which shares the largest part of its grammar and vocabulary with Norwegian, has even fewer deponents, which work basically like in the other Scandinavian languages; the only common ones are:
Some other verbs do have an active form but also a deponent one with a different meaning or usage, e.g.:
Finally, some verbs are passive in Danish, but would be translated with active verbs in most other languages, e.g.:
Deponency and tense.
Some verbs are deponent universally, but other verbs are deponent only in certain tenses, or use deponent forms from different voices in different tenses. For example, the Greek verb ἀναβαίνω ("anabaino") uses active forms in the imperfect active and aorist active, but in the future active it shows the middle form ἀναβήσομαι ("anabesomai"). The future active form might be predicted to be *ἀναβήσω ("anabeso"), but this form does not occur, because the verb is deponent in the future tense. The future forms that do occur have the same meaning and translation value that the active forms would have if they occurred.
Latin has a few semi-deponent verbs, which behave normally in the present system, but are deponent in the perfect system.