Passed by is a verb.
If you use a noun liked passers by, that means a number of people walking by. I am not aware of a singular version of that.
The plural form of the word atrium is atria. The atria are the two upper cavities of the heart from which blood is passed to the ventricles.
The word bus is a noun. The plural form is buses.
The word crises is a plural word; it is the plural form of the word crisis.
There is no plural word for if.
The plural form for the demonstrative pronoun this is these.
A non-plural word, a word (noun or pronoun) that is not plural is singular, a word for just one.
The plural word of delay is delays.
the plural word is comedones
No it's a singular word. A plural word would be "have".
Leukocytes is the plural of leukocyte
The plural of "classification" is "classifications."
The plural noun is raisins.