This is the 4171st most frequent Chinese word.
唯独
"唯独" means "only" or "except for."
Here, '唯独' is used to highlight Xiaoming as the exception within a group of students.
在所有的学生中,唯独小明不愿意参加比赛。
Among all the students, only Xiaoming is unwilling to participate in the competition.
In this sentence, '唯独' emphasizes that the map is the specific item that was neglected among others.
这次旅行带了很多东西,唯独忘了地图。
For this trip, many things were brought, but the map was forgotten.
This usage of '唯独' draws attention to the absence of food ingredients despite everything else being prepared.