I'm not sure I understand how "come away" would be lumped with the other two here. When I think of usage, I think of things like "When I have a Japanese class late in the evening, I come away from the experience feeling saturated and confused." It roughly means "leave the situation (with something, feeling something, etc.)". Do you have an example for this that illustrates your confusion? "Come apart" means to separate/come undone/break down naturally or without external help. For example: "I bought a pair of jeans that I thought were a bargain, until the seams came apart after one washing." - The jeans fell apart after one laundry washing; I didn't do anything to them to make them come undone. To dismantle is to *actively* or *consciously* take something apart. Example: I dismantled the telephone to see how it worked, but then I couldn't figure out how to put it back together. - In this case, the telephone didn't just "naturally" come apart; I took it apart *on purpose* to see how it worked.

Come apart = disintegrate or can break into smaller pieces Come away from = detach itself from another object gradually or because of a process Dismantle = actively take something apart, reduce it to its components Find example sentences eg on fraze.it