“先生” （xiān sheng）Vs“老师”(xiānsheng)
You may hear Chinese people call a teacher “先生（xiān sheng）” in a university. But you will never hear a person do such introduction to his teacher.
“这是我先生”(zhè shì wǒ xiānsheng). This sentence is not the meaning of “This is my teacher” or “This is my professor”. In fact, it means “This is my husband”.“先生”(xiānsheng) has three meanings in Chinese.The first one is an appellation only for the teachers who have a higher level of knowledge. In this situation, “先生” has the same meaning as “老师”(lǎoshi)—teacher.For example:
“王先生教我们汉语” (wáng xiān sheng jiāo wǒ mēn hàn yǔ)—–Teacher Wang teaches us Chinese.
他是我先生(tā shì wǒ xiānsheng)——He is my husband.
你先生在哪儿工作？(nǐ xiānsheng zài nǎ ér gōng zuò)—–Where does your husband work?