Learners often think they’re synonyms because dictionaries list “though” as translation for both of them. But the two words have completely different grammatical functions in German.
Obwohl is a so called into-word. So it is one of those words that create a sentence with all the verbs at the end in German.
- Obwohl ich heute keine Lust habe, mache ich Sport.
- Even though/ although I don’t have energy today, I work out.
trotzdem is an adverb and it works exactly the same way as the da-words like danach or darum. It can be at the beginning or in the middle of a sentence.
The best translation is despite that.
- Ich habe heute keine Energie. Trotzdem habe ich Sport gemacht.
- I have no energy today. Despite that I worked out today.
For a closer look, check out my article about “trotzdem”. There, you’ll also learn about “trotz” and we’ll do a couple of exercises that aren’t hard at all… (actually, they’re really really hard. I need to make them easier. Nerd level 9)
Also interesting:
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A fun look at the meaning and origin of "trotzdem" and a breakdown of when to use "trotz", "trotzdem" and "obwohl". Of course with audio examples :)
Vocab:
trotzdem, obwohl, der Trotz, trotzen, trotz

tak jsi piča ani mi to nevysvětlíš
Forgot to add the link to my article. Thanks for this, it was actually helpful. But why the insults, why so angry?