the plural word is comedones
comedo
A blackhead, or open comedo is a wide opening on the skin with a blackened mass of skin debris covering the opening. Despite their name, some blackheads can be yellowish in color. A comedo is a widened hair follicle which is filled with skin debris (keratin squamae), bacteria and oil (sebum). A closed comedo is a whitehead, while an open comedo is a blackhead. the plural of "comedo" is comedomes".
When the sebum plug of a comedo is exposed to air, it oxidizes and becomes a blackhead.
According to the NIH, it is called a comedo.
Bridges is the plural form of bridge.
"Groceries" is the plural form of "grocery."
There is no plural form for the word, countries. This word itself is a plural.
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.
The plural form of "meter" is "meters."
It has no plural form.
The plural form for the noun sergeant is sergeants; the plural possessive form is sergeants'.