This is the 6260th most frequent Japanese word.
グレープフルーツ
Grapefruit.
Here, 'グレープフルーツ' is used as a direct object, specifying the item consumed during breakfast.
朝ごはんにグレープフルーツを食べました。
I ate a grapefruit for breakfast.
In this case, 'グレープフルーツ' serves as a descriptor in the compound noun 'グレープフルーツジュース', indicating the type of juice.
グレープフルーツジュースを飲むのが好きです。
I enjoy drinking grapefruit juice.
Here, 'グレープフルーツ' functions as the subject of the sentence, which is being described by the adjective '大きい' (large).