1.
Monday; Mon.
The clipped form of 月曜日, used where the day is already understood as a day of the week — schedules, timetables, calendars, and casual speech.
Shortened from 月曜日 by dropping 日. The full form is the default in careful speech and writing; the short form appears where space is tight or the context is obvious.
Common collocations
Usage
All seven days clip the same way (火曜, 水曜, 木曜, 金曜, 土曜, 日曜). In tables and signs the reading is often abbreviated further to the single kanji 月.