To subdivide something is to cut into smaller pieces something that has already been cut up once. The 'sub-' carries that second step: you divide a book into chapters, then subdivide each chapter into sections. You divide a country into regions, then subdivide the regions into districts. If you are only cutting something whole for the first time, 'divide' is the word you want. It shows up in three places especially. In writing and organising: 'The report is subdivided into four parts.' In land and property, where it is close to a technical term — a farmer subdivides a large field into smaller plots to sell for houses, and in American English the noun 'a subdivision' has come to mean a whole housing estate built that way. And in science and classification: cells subdivide, categories are subdivided into types. It is often used in the passive ('the class was subdivided into groups of three'), which is a comfortable pattern to learn. The word is a little formal — in casual speech you would probably just say 'split it up again' or 'break it down further'.

再細分、細分成更小的部分；土地方面就是「分割（土地）」。