This is the 1897th most frequent Japanese word.
築い
"築い" is not a standalone word, but likely a conjugation of "築く" (kizuku), which means "to build" or "to construct."
築い is used in its past tense form '築いた' to mean 'built' in the sense of building an abstract concept like trust.
彼は長年かけて信頼を築いた。
He built trust over many years.
築い is used in its base verb form '築く' to mean 'to build' with respect to creating or establishing a home or family.
彼女は家庭を築くことが夢だった。
Her dream was to build a household.
築い is used as '築いている,' a progressive form, to describe actively establishing or laying out a foundation, emphasizing an ongoing process.