General:
* Un sujet profond: This is the most direct translation and is generally understood.
* Un sujet sérieux: This emphasizes the seriousness and importance of the subject.
More specific:
* Un sujet complexe: This highlights the intricate nature of the subject.
* Un sujet difficile: This suggests that the subject is challenging to understand or discuss.
* Un sujet qui soulève des questions profondes: This implies that the subject prompts deep reflection and philosophical thought.
Example Sentences:
* "C'est un sujet profond que je ne comprends pas encore complètement." (This is a deep subject that I don't fully understand yet.)
* "Le changement climatique est un sujet sérieux qui exige notre attention." (Climate change is a serious subject that demands our attention.)
* "La philosophie est un sujet complexe qui a fasciné les penseurs pendant des siècles." (Philosophy is a complex subject that has fascinated thinkers for centuries.)
* "L'amour est un sujet difficile qui peut être source de joie et de douleur." (Love is a difficult subject that can be a source of joy and pain.)
* "La mort est un sujet qui soulève des questions profondes sur la vie et la mort." (Death is a subject that raises profound questions about life and death.)
The best way to choose the right phrase depends on the specific context and your intended meaning.