General prefixes:
* pre- (before): preform (to shape or mold in advance)
* re- (again): reform (to improve by changing)
* un- (not): unformed (not shaped or developed)
* de- (remove, reverse): deform (to change the shape of something, often for the worse)
* multi- (many): multiform (having many shapes or forms)
* bi- (two): biform (having two forms)
More specific prefixes:
* auto- (self): autoform (a self-forming process)
* geo- (earth): geoform (a landform)
* bio- (life): bioform (a living organism)
* thermo- (heat): thermoform (to shape plastic using heat)
* electro- (electricity): electroform (to deposit metal on a mold using electricity)
* stereo- (solid, three-dimensional): stereoform (having a solid, three-dimensional form)
These are just some examples, and the specific prefix you choose will depend on the context.