耐心(nài xīn) - patience; patient in Mandarin

耐心 (nài xīn) is patience. It behaves as a noun, so you have it or you lack it: 很有耐心 is very patient, 没有耐心 is impatient, and 失去耐心 is to lose patience.

It doubles as an adverb once you add 地: 耐心地听, 耐心地解释. The person you are being patient with is introduced by 对, so 他对学生很有耐心 is he is very patient with his pupils.

The trap is the copula. English turns patience into an adjective and says "he is patient", which tempts learners into 他是耐心. Chinese keeps it a noun and needs the verb 有: 他很有耐心. Get that reflex in early, because the same shape covers 有信心, 有兴趣 and 有意思.