come up指走上前去（如：The policeman come up and ask the man a few question.警察走上前去，问了那个男人几个问题），come up with指想出（如：come up with some ideas.想出了几个点子）。

come up大都指实际上的走进，如I came up my bus to work.我赶上了去上班的公交；come up with指思想、习惯等的赶上，如：I came up with the teacher's thoughts and understand a lot.我跟上老师的思想节奏，明白了许多。