女友 (nǚyǒu) is a noun meaning "girlfriend." It is a slightly more formal or written alternative to 女朋友 (nǚ péngyou). The male counterpart is 男友 (boyfriend). It is commonly used in news reports and written Chinese.
他和女友在一起三年了,打算明年结婚。
tā hé nǚyǒu zài yīqǐ sān nián le, dǎsuàn míngnián jiéhūn.
He's been with his girlfriend for three years and plans to get married next year.
听说他新交了一个女友,是他同事。
tīngshuō tā xīn jiāo le yī gè nǚyǒu, shì tā tóngshì.
I heard he recently got a new girlfriend; she's his colleague.
他送了女友一束花当生日礼物。
tā sòng le nǚyǒu yī shù huā dāng shēngrì lǐwù.
He gave his girlfriend a bouquet of flowers as a birthday gift.