Subject + 恋爱 / 谈恋爱
The verb 恋爱 (liàn'ài) means "to be in love" or "to have a romantic relationship." It describes the state or process of being romantically involved with someone. A common expression is 谈恋爱, meaning "to date" or "to be in a relationship."
他们谈恋爱已经三年了,感情很好。
Tāmen tán liàn'ài yǐjīng sān nián le, gǎnqíng hěn hǎo.
They've been dating for three years now, and their relationship is very good.
大学的时候她不想恋爱,只想好好学习。
Dàxué de shíhou tā bù xiǎng liàn'ài, zhǐ xiǎng hǎohǎo xuéxí.
When she was in college, she didn't want to date — she just wanted to study hard.
我姐姐正在和一个医生谈恋爱。
Wǒ jiějie zhèngzài hé yī gè yīshēng tán liàn'ài.
My older sister is currently dating a doctor.