break down means 1) get upset or to be unable to control emotions (e.g. The woman broke down when we gave her the bad news.) 2) stop relationships (e.g. Ann’s marriage broke down after only a few weeks.) 3) stop working (for machines, cars etc.) (e.g. Sorry for late come because my car was broken down.)
break something down means divide into smaller parts (e.g. We should break the project down into a couple of areas.)

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