Soprano- the range from "About" middle C to two octaves above it.

I am checking the OED as I look these up and it takes a lot of flipping and changing from volume to volume; a singer probably has references that give the definitions all together.

Remember that any particular singer may differ; that is why the definitions have modifiers like 'about, or 'generally.' Most of us go by 'ear,' when we say a singer is a bass, or a tenor, or mezzo-soprano, etc.