noun

The lowest part or edge of something, especially the part on which it rests or is supported.

she sat down at the base of a tree

foundation,bottom,foot,support,prop,stay,stand,pedestal,plinth,rest,bed,substructure

verb

Use (something specified) as the foundation or starting point for something.

the film is based on a novel by Pat Conroy

found,build,construct,form,establish,ground,root