This is the 9111th most frequent Japanese word.
火曜
Tuesday.
The use of 火曜日 (Tuesday) identifies the specific day when the event takes place.
火曜日はミーティングがあります。
There is a meeting on Tuesday.
Here, 火曜日 serves as an adverbial noun indicating the timing of the exam.
試験は火曜日に行われます。
The exam will be held on Tuesday.
In this sentence, 火曜 refers to the plan or events belonging to Tuesday.