This is the 3599th most frequent German word.
montagnachmittag
Monday afternoon.
'Montagnachmittag' here indicates the time for the planned activity without a preceding preposition.
Wir treffen uns Montagnachmittag zum Kaffee.
We meet on Monday afternoon for coffee.
Here, 'montagnachmittag' is used as a noun denoting a specific time of the week—the afternoon of Monday.
Montagnachmittag gehe ich oft spazieren.
Monday afternoon I often go for a walk.
In this sentence, 'montagnachmittag' is preceded by 'am', indicating the time frame during which the action occurs.