Nouns as attributes are generally singular, but there are some exceptions:

Use the plural as the attributive, for example, the foreign language department of the student reading room of the sports meeting.

Be a man, a woman, a gentleman, etc. As attributes, their singular and plural depend on the singular and plural of the nouns they modify, for example, male workers and female teachers.

When some nouns ending in s are used as attributes, s is reserved, for example, freight train customs clearance.

When numerals+nouns are used as attributive, the noun generally keeps singular form, for example, two dozen eggs/twenty-four eggs walk ten miles (some individuals also use plural as attributive, such as a seven-year-old child).