यक़ीन (yaqiin)

noun A single core sense: 'belief, certainty, trust' -- most often met in the phrase यक़ीन करना (yaqiin karnaa, 'to believe') and यक़ीन होना (yaqiin honaa, 'to be certain/convinced').
Sense 1 : belief, certainty, conviction, trust
noun, masculine Typically used with करना (karnaa) for 'to believe' (यक़ीन करना, yaqiin karnaa) and with होना (honaa) or आना (aanaa) for 'to become convinced' (यक़ीन होना/आना, yaqiin honaa/yaqiin aanaa), the latter often with a को-marked experiencer: मुझे यक़ीन है (mujhe yaqiin hai, 'I am certain').
Synonyms: विश्वास (vishvaas), भरोसा (bharosaa, trust, esp. reliance on a person), एतबार (etbaar, colloquial)
Frequency: high
Cultural Note: यक़ीन (yaqiin) is an Urdu-origin word that has become completely everyday in Hindi speech -- you will hear it constantly in Bollywood dialogue and casual conversation alike, often paired with दिलाना (yaqiin dilaanaa, 'to convince/assure someone'). Note the nuqta under क़ (q); dropping it (यकीन, yakiin) is extremely common in casual writing and perfectly acceptable.
Common Mistakes: 1) Learners often reach for विश्वास (vishvaas) in every context, but यक़ीन (yaqiin) is the word of choice in everyday spoken Hindi, especially in Delhi -- विश्वास can sound a touch more formal or written. 2) The experiencer of belief is usually marked with को (ko) (मुझे यक़ीन नहीं होता, mujhe yaqiin nahiin hotaa, 'I can't believe it'), not with ने (ne), even though यक़ीन करना is transitive and takes ने in past tense (उसने यक़ीन किया, usne yaqiin kiyaa).
Sample Sentences:
मुझे तुम पर पूरा यक़ीन है। I have complete trust in you.
(mujhe tum par pooraa yaqiin hai।)
Register: Casual -- Mood: Indicative -- Tense: Present -- Voice: Active
मुझे यक़ीन नहीं हो रहा कि तुमने ये कर दिया। I can't believe you actually did this.
(mujhe yaqiin nahiin ho rahaa ki tumne ye kar diyaa।)
Register: Casual -- Mood: Indicative -- Aspect: Continuous -- Tense: Present -- Voice: Active
उसने मुझे यक़ीन दिलाया कि वह वक़्त पर आएगा। He assured me that he would come on time.
(usne mujhe yaqiin dilaayaa ki vah vaqt par aaegaa।)
Register: Neutral -- Mood: Indicative -- Aspect: Perfective -- Tense: Past -- Voice: Active
अगर तुम मुझे सबूत दिखाओ, तो शायद मुझे यक़ीन आ जाए। If you show me proof, maybe I'll come to believe it.
(agar tum mujhe saboot dikhaao, to shaayad mujhe yaqiin aa jaae।)
Register: Neutral -- Mood: Subjunctive -- Voice: Active
अगर उसे मुझ पर यक़ीन होता, तो वह ऐसे सवाल न पूछता। If he trusted me, he wouldn't ask such questions.
(agar use mujh par yaqiin hotaa, to vah aise savaal n poochhtaa।)
Register: Neutral -- Mood: Counterfactual -- Aspect: Habitual -- Voice: Active
कृपया मुझे यक़ीन दिलाइए कि यह जानकारी सही है। Please assure me that this information is correct.
(kripyaa mujhe yaqiin dilaaie ki yah jaankaarii sahii hai।)
Register: Formal -- Mood: Imperative -- Voice: Active
बचपन से ही उसे भगवान पर गहरा यक़ीन रहा है। He has had a deep faith in God since childhood.
(bachpan se hii use bhagvaan par gahraa yaqiin rahaa hai।)
Register: Neutral -- Mood: Indicative -- Aspect: Perfective -- Tense: Present -- Voice: Active
यह बात सुनकर उसका यक़ीन टूट गया। Hearing this, his conviction was shattered.
(yah baat sunkar uskaa yaqiin toot gayaa।)
Register: Literary -- Mood: Indicative -- Aspect: Perfective -- Tense: Past -- Voice: Active
उम्मीदवार को यह यक़ीन दिलाया गया कि उसकी नौकरी पक्की है। The candidate was assured that his job was confirmed.
(ummiidvaar ko yah yaqiin dilaayaa gayaa ki uskii naukrii pakkii hai।)
Register: Formal -- Mood: Indicative -- Aspect: Perfective -- Tense: Past -- Voice: Passive
अरे यार, यक़ीन मानो, मैंने सच में लॉटरी जीती है! Dude, believe me, I actually won the lottery!
(are yaar, yaqiin maano, mainne sach men lotrii jiitii hai!)
Register: Casual -- Mood: Imperative -- Voice: Active
काश मुझे भी अपने आप पर उतना ही यक़ीन होता। I wish I had that much confidence in myself too.
(kaash mujhe bhii apne aap par utnaa hii yaqiin hotaa।)
Register: Neutral -- Mood: Counterfactual -- Aspect: Habitual -- Voice: Active
Morphology
Noun
(sg.m.direct): यक़ीन (yaqiin)
(sg.m.oblique): यक़ीन (yaqiin)
(pl.m.direct): यक़ीन (yaqiin)
(pl.m.oblique): यक़ीनों (yaqiinon)