1The family name or surname — the portion of one's name inherited from one's family (e.g., 田中, 鈴木, 佐藤 in Japan), as opposed to the given name (下の名前). Both 名字 and 苗字 are correct; 名字 is somewhat more common in modern writing. Historically, 名字 was used in the Heian period for noble family names, while 苗字 became widespread in the Edo period.
私の名字は田中、下の名前は健一です。
My family name is Tanaka, and my given name is Ken'ichi.
日本では結婚すると、夫婦のどちらかが名字を変えなければならない。
In Japan, when a couple gets married, one of them is required to change their family name.
「佐藤」は日本で一番多い名字だそうだ。
Apparently, Sato is the most common family name in Japan.
書類には名字と名前を分けてお書きください。
Please write your family name and given name separately on the form.
彼女は仕事では旧姓の苗字を使い続けている。
She continues to use her maiden name at work.