there are 0 cats in the room. there are 3 cats in the room. The phrase "there is 1 cat in the room" is an example of plural's counterpart, singular.
Two halves are better than
one, even though two halves is equal to
one. While
one half is singular, two halves is plural.
And we wouldn't say "two halves are plural".
Yet, two halves are one, is fine.