The noun 基础 (jīchǔ) means "base," "foundation," or "basis." It can refer to physical foundations or abstract concepts like the basis of knowledge or a system. It is widely used in expressions like 基础知识 (basic knowledge) and 以...为基础 (based on...).
学好基础知识对以后的学习非常重要。
Xué hǎo jīchǔ zhīshi duì yǐhòu de xuéxí fēicháng zhòngyào.
Learning the fundamentals well is very important for future studies.
这栋楼的基础打得很牢固,不用担心安全问题。
Zhè dòng lóu de jīchǔ dǎ de hěn láogù, bùyòng dānxīn ānquán wèntí.
The foundation of this building was laid very solidly, so there's no need to worry about safety.
我们的合作是以互相信任为基础的。
Wǒmen de hézuò shì yǐ hùxiāng xìnrèn wéi jīchǔ de.
Our cooperation is based on mutual trust.