Conversion of Voice
स्वर का रूपांतर
Points to be considered when converting active voice to passive voice...
सक्रीय स्वर से निष्क्रीय स्वर में रुपांतरित करते समय निम्न बिंदुओं पर गौर करें...
Tense of the Verb
The Passive is formed by putting the verb to be in the same tense as in the active form.
निष्क्रीय बनाने के लिये, सक्रीय स्वर का जो काल है, उसी काल का to be क्रिया का रूप डाला जाता है.
Active Form: play.
Passive Form: is played.

Subject to Object
The subject of active verb becomes the object of the passive verb, and often the object is not mentioned.
स्क्रीय क्रिया का कर्ता, निष्क्रीय क्रिया का कारक बन जाता है, और अक्सर इस कारक का उल्लेख नहीं किया जाता.
Active Form: People have seen animals in the street.
Passive Form: Animals have been seen in the street.

Use of By
Whenever the object is mentioned, it is preceded by by.
जब भी कारक का उल्लेख किया जाता है, उसके पहले by शब्द जोड़ा जाता है.
Active Form: My father planted this tree.
Passive Form: This tree was planted by my father.

Some Active Tenses and their Passive equivalents for: sell
Tense Active Form Passive Form
Simple Present sells is sold
Simple Past sold was sold
Simple Future will sell will be sold

Examples:
Tense Active Voice Passive Voice
Present Ram sells vegetables. Vegetables are sold by Ram.
Past Kiran sold the book. The book was sold by Kiran.
Future Rama will sell her phone. Her phone will be sold by Rama.

Perfect Tense and Continuous Tense
The passive of continuous tense and perfect tense requires that use of the same tense form of the to be.
पूण या र्अपूर्ण काल के निष्क्रीय रूप बनाने के लिये to be का वही काल का रूप लगता है.

Tense Active Form Passive Form
Present Continuous is selling is being sold
Present Perfect has sold had been sold
Past Continuous was selling was being sold
Past Perfect had sold had been sold


The other perfect tense, continuous tense and perfect continuous tense are very rared used in the passive voice.
बाकी के पूर्ण काल, अपूर्ण काल और सतत् पूर्ण काल वाले सक्रीय स्वर को बहुत कम बार निष्क्रीय रूप में रूपांतरित किया जाता है.

Some Active Verb Forms and their Passive equivalents for: sell
Verb Form Active Form Passive Form
Present Infinitive to sell to be sold
Perfect Infinitive to have sold to have been sold
Present Participle / Gerund selling being sold
Perfect Participle having sold having been sold

Use of prepositions instead of By
There are cases when you use some preposition in place of by before the doer of the action to form the passive voice.
कुछ प्रकरण ऐसे भी होते हैं जिनमें निष्क्रीय स्वर बनाने के लिये कार्य करने वाले के पहले by के स्थान पर कोई सम्बन्ध सूचक-अव्यय का उपयोग किया जाता है.
Active Form: Smoke filled the room.
Passive Form: The room was filled with smoke.

For more on use of Prepositions in passive voice click here.
निष्क्रीय स्वर में सम्बन्ध सूचक-अव्यय पर अधिक जानकारी के लिए यहाँ क्लिक करें.

Active & Passive Conversion Usage Role of Prepositions