noun
Refers to a physical foundation (of a building, structure) or a figurative basis (of an argument, system, relationship).
家の土台がしっかりしていないと、地震で倒れてしまう。
If the foundation of the house is not solid, it will collapse in an earthquake.
信頼は良い関係の土台だ。
Trust is the basis of a good relationship.
adverb
from the beginning; by nature; originally
Used adverbially, often in negative contexts, to mean 'in the first place' or 'fundamentally'. Similar to 元々, but with a nuance of inherent impossibility or unsuitability.
See also: 元々
彼は土台、人前で話すのが苦手だ。
He is, by nature, not good at speaking in public.
その計画は土台無理だった。
That plan was impossible from the outset.