第一 + (Measure Word) + Noun
第一 (dìyī) is an ordinal number meaning 'first' or 'number one.' It is formed by placing 第 before the number 一 and is used to indicate rank, order, or sequence. It can modify nouns directly or be followed by a measure word.
她是班里第一个交作业的学生。
tā shì bān lǐ dì yī gè jiāo zuòyè de xuéshēng.
She was the first student in the class to turn in her homework.
安全永远是第一位的。
ānquán yǒngyuǎn shì dì yī wèi de.
Safety always comes first.
这是我第一次来中国。
zhè shì wǒ dì yī cì lái zhōngguó.
This is my first time visiting China.