jungle is like dnb, except it's harder, faster, has less melody, has crazy samples etc
dnb has more 'techno' (i use that word loosely) elements, some buildups and stuff, along with its customary beats etc. usually has some ambient fx, much more atmospheric, sometimes with vocals.

edit: kinda think of it this way... trance is to hardstyle, what dnb is to jungle. jungle is way more in your face like hardstyle, and dnb can have some awesome melodies like trance etc.

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