【Base】 , 【found】 , 【ground】 , 【bottom】 , 【stay】 , 【rest】 are comparable when they mean to supply or to serve as a basis.

【Base】 now rarely suggests a material support upon which a material superstructure is built, but rather something material or immaterial that underlies a nonmaterial superstructure (as a belief, a system, a judgment, a hope or an action).

【Found】 comes so close to 【base】 as often to be indistinguishable from it and, therefore, to be interchangeable with it.

Often, however, it suggests not what merely underlies but what is consciously advanced as support (as for an opinion, a principle, a judgment, a belief, or an affection).

【Ground】 denotes an implanting (as into the earth) that gives solidity and firmness; it may apply to something (as personal virtue, education, or an institution) which can grow and thrive only when it is firmly based (as if by deep roots).

But 【ground】 may be used, less strictly, in a sense approaching that of 【base】 and 【found】 .

【Bottom】 implies a broad or strong 【base】 .

【Stay】 implies a support that keeps upright or prevents from falling and may suggest adding a supplementary support to correct an observed or anticipated tendency.

【Rest】 stresses reliance or dependence on something as a 【base】 or fundamental support.