ermüdend
tiring
Physically or mentally demanding and making you tired.
Die lange Wanderung durch die Berge war sehr ermüdend.
The long hike through the mountains was very tiring.

tiring
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tiring
Physically or mentally demanding and making you tired.
Die lange Wanderung durch die Berge war sehr ermüdend.
The long hike through the mountains was very tiring.

'Ermüdend' (tiring) is the present participle of the verb 'ermüden' (to tire). It describes an activity or thing that has the quality of making you tired. Many German adjectives are formed this way with the ending '-end'.
Die stundenlange Autofahrt im Stau war sehr ermüdend.
The hours-long car ride in traffic was very tiring.
The adjective 'müde' (tired) is contained in the word 'ermüdend' (tiring). The prefix 'er-' here expresses that something is brought into the state of being 'müde' (tired). Recognizing 'müde' helps with understanding.
Diese sich ständig wiederholende Aufgabe ist wirklich ermüdend.
This constantly repeating task is really tiring.
Whether 'ermüdend' (tiring/tedious) means physical exertion or mental monotony is revealed by the context. With physical activities like 'Wanderung' (hike), it is about physical tiredness. With 'Diskussion' (discussion) or 'Vortrag' (lecture/presentation), it usually refers to mental fatigue caused by boredom.
Das Training war kurz, aber sehr ermüdend.
The training session was short but very tiring.
In the sense of physically demanding, 'ermüdend' (tiring) is often connected with activities or conditions. Typical phrases are 'eine ermüdende Reise' (a tiring journey), 'ein ermüdender Aufstieg' (a tiring climb), or 'eine ermüdende Arbeit' (tiring work).
Nach dem ermüdenden Aufstieg genossen wir die Aussicht vom Gipfel.
After the tiring climb, we enjoyed the view from the summit.
When 'ermüdend' (tedious) describes boredom, it is often used with nouns related to mental processes or communication. Common phrases are 'eine ermüdende Debatte' (a tedious debate), 'ein ermüdender Film' (a tedious film), or 'ermüdende Routineaufgaben' (tedious routine tasks).
Das Warten in der Schlange war eine ermüdende Erfahrung.
Waiting in line was a tedious experience.
boring
'langweilig' and 'ermüdend' can both fit situations that you do not find pleasant. 'langweilig' mainly means: there is a lack of interest or variety. 'ermüdend' emphasizes more strongly that something makes you tired or becomes mentally exhausting. This can happen because of boredom, but also because of a lot of work, long conversations, or difficult tasks. If something is simply uninteresting, you are more likely to say 'langweilig'. If something drains your energy over time, 'ermüdend' is more precise.

Nach drei Stunden war die Diskussion für alle ermüdend.
After three hours, the discussion was tiring for everyone.
Ich finde den Termin langweilig, weil immer nur dieselben Punkte besprochen werden.
I find the appointment boring because only the same points are discussed every time.