"The tenth egg is not mine."
Translation:Onuncu yumurta benim değil.
"değil" on it's own is 3rd person singular - "it/he/she is not";
"değilim" = "I am not"
So in this sentence, we are not negating ourselves: "I am not the tenth egg". (Haha!) We are negating the egg being mine. An egg is an "it" so we use plain "değil". It might help if we change the adjective to something else for comparison:
- Onuncu yumurta benim değil. = the 10th egg is not mine.
- Onuncu yumurta büyük değil. = the 10th egg is not large.
I know you waited a long time for a response, but hopefully that helps you or someone with the same question :-)
There is no need for a possessive on the 10th. "Onuncu" is an adjective, so we can just place it in front of the noun we are modifying without any suffixes:
- Onuncu yumurta benim değil. = The 10th egg is not mine.
- Yeşil yumurta benim değil. = The green egg is not mine.
- Küçük yumurta benim değil = The small egg is not mine.
Possessive construction would create: "The egg of the 10th" or "The 10th's egg", which doesn't make sense. :-)
- değilim = I am not
- değil = he/she/it is not
- Yumurta değilim. = I am not an egg.
- Yumurta benim değil. = The egg is not mine.
In Duo's sentence, we are saying that the egg is not mine. "The egg" is an "it," so we will use 3rd-person, which has no suffix at all: değil. I hope that helps. :-)