There is only one word in the English language that both singular and masculine becomes plural when you place an S at end add another it reverts to but then turns?

Here's why:

* Singular: bus

* Plural: buses

* Adding another 's': busses (this is an archaic plural form, rarely used)

* Reverting to singular: buss (an old word for kiss)

* Turns: The word "buss" is also a verb meaning "to kiss."

Let me know if you'd like to try another riddle!