"Your book was on the table."

Translation: तेरी किताब मेज़ पर थी।

[Aakhil6]

Please use tumhari than teri .
Atleast show some formality in Duolingo.
Urdu always defaults it as aapki that's the level of respect in Urdu.
But what is that teri in Hindi

[Chris873772]

Agreed. Someone learning the language should master polite forms first.

[wwe10on10]

One can use either teri or tumhari, if u are conversing in a formal manner u will say tumhari or aapki but if u r in an informal situation u would say teri and that is also optional, this is the shortcomings of the Duolingo or a computer that it can't correct either way।।।।
And if u want to meet formality then learn sanskrit, u know pānini created sanskrit grammar and none of the languages in the world has correct grammar than of pānini's sanskrit grammar

[Akihsi7]

What's the difference between थी and थीं?

[Hiba-al-Sayf]

They're both feminine. The latter is the plural, but like in French, the plural is also used in formal speech. Ditto for masculine forms था/تھا (sing.) & थे/تھے (pl. or sing. f.)

[AndriLindbergs]

I decided to try using the non-Urdu पुस्तक instead of the Urdu किताब and I was happy that they accepted it.

[emrys29]

Kitaab is as much Hindi as it is Urdu. You'll find kids of all ages using it in the Hindi belt of India. पुस्तक is only used in formal settings. Everywhere else we use किताब. :)

[wwe10on10]

Sorry, but, kitaab is clearly an urdu word and its hindi words would be kitaab। But it is shortcomings of our system that we use urdu in writing of Hindi

[wwe10on10]

That's a good spirit
What i personally think that one should learn a second language in its true form

[Hiba-al-Sayf]

The differences between "Urdu" and "Hindi" are more a product if artificial purism than a natural difference, and the spoken register is the same anyhow.

[tizerzert]

And how would we say : your book used to be on the table?

[Hiba-al-Sayf]

आप की किताब मेज़ पर (रखी) होती थी/آپ کی کتاب میز پر (رکھی) ہوتی تھی
I'd refer to my other comment here on why I'm using आप की/آپ کی instead of तेरी/تیری. Also, in colloquial speech, you may hear पे/پہ instead of पर/پر.

[Hiba-al-Sayf]

Duolingo should probably use आप की/آپ کی (f.) or तुम्हारी/تمہاری (inf.) when teaching these phrases.
तेरी/تیری is extremely informal and borderline offensive unless possibly among very close friends (Then again, I've never used it with mine).
I should probably mention here that the most formal (आप/آپ) is always safe, no matter how well you know the other person.