"He bought an apple for the new kitchen."
Translation:Mi brynodd e afal i'r gegin newydd.
Yes cegin is feminine, so in the sentence above 'i'r gegin', 'for the kitchen' cegin has become 'gegin' after the definite article. Are you referring to 'y cegin' somewhere else in the course? If so it's another example of the zombie sentences that Duolingo doesn't seem to be able to remove.
We deleted this sentence because of the two fundamental errors in the Welsh to English part.
'Mi brynodd e' is an incorrect mixing of the North Wales verb and the South Wales pronoun.
i'r cegin is incorrect because 'cegin' is a feminine noun.
It's a zombie sentence that has yet to be deleted from the system because of a system wide bug which Duolingo is struggling to resolve.