Postposition के बाद (

Think of a postposition (like mein - in, or ko - to) as a heavy weight. When you place it *after* a noun, that noun has to "bend" or change shape to support it. This bent shape is the Oblique form. You never use this form on its own; it exists *only* to support the postposition. It’s a symbiotic relationship. If the postposition disappears, the noun snaps back to its original form.

1. 1Here is the cheat sheet for how to bend your nouns into the Oblique Case:
2. 2Masculine Singular (-aa ending): The -aa changes to -e.
3. 3Kamra (Room) + mein → Kamre mein (In the room)
4. 4Beta (Son) + ko → Bete ko (To the son)
5. 5Masculine Singular (Other endings): No change! They stay strong.
6. 6Ghar (House) + par → Ghar par (At home)
7. 7Dost (Friend) + se → Dost se (With friend)
8. 8Feminine Singular (Any ending): No change! They are stubborn.
9. 9Mez (Table) + par → Mez par (On the table)
10. 10Ladki (Girl) + ko → Ladki ko (To the girl)
11. 11Masculine Plural: The ending changes to -on.
12. 12Ladke (Boys) + ko → Ladkon ko (To the boys)
13. 13Ghar (Houses) + mein → Gharon mein (In the houses)
14. 14Feminine Plural: The ending changes to -on.
15. 15Ladkiyan (Girls) + se → Ladkiyon se (From the girls)
16. 16Kitabein (Books) + mein → Kitabon mein (In the books)

You use this every single time a noun or pronoun is followed immediately by a postposition. It doesn't matter if it's a simple postposition (ko, se) or a compound one (ke baad, ke saath, ke liye). If the postposition is there, the noun *must* be in the oblique case. It's like a toll booth; you can't pass the postposition without paying the "oblique" toll.

Do not use the Oblique case if there is no postposition! This is common when the noun is the Subject of the sentence (and not followed by ne).

• Correct: Ladka khel raha hai (The boy is playing). Here, Ladka is just the subject. No ko, no se, so no change.
• Incorrect: Ladke khel raha hai (unless you mean plural, but even then, syntax matters).

The biggest mistake learners make is forgetting to change the Adjectives too! Yes, if the noun changes, the adjective describing it must also change.

• Wrong: Bada kamre mein (In the big room) ✗
• Correct: Bade kamre mein ✓
• Think of it as peer pressure. If the noun changes clothes, the adjective has to match the outfit.

In English, we use prepositions (words *before* the noun: "in London"). In Hindi, we use postpositions (words *after* the noun: "London mein"). English pronouns change case too (He -> Him, Who -> Whom), but Hindi does it for *nouns* as well. Also, be careful not to confuse the Oblique plural (Ladkon) with the direct plural (Ladke). Ladke is for "The boys are here." Ladkon is for "To the boys."