久美子

In a sentence

• 久美子さんは教師です。

  Ms. Kumiko is a teacher.

  Here, 久美子 is used as a proper noun referring to an individual's name, followed by さん, which is a polite honorific.

• 久美子は学校へ行きました。

  Kumiko went to school.

  In this sentence, 久美子 acts again as a proper noun referring to an individual, without a polite title like さん following it, making the usage slightly casual.

• 昨日、久美子という女性に会いました。

  Yesterday, I met a woman named Kumiko.

  Here, 久美子 is positioned as a quoted proper noun within the construction 久美子という女性 which means 'a woman called Kumiko,' introducing the name within descriptive context.