<P> The metre ( British spelling ) or meter ( American spelling ) ( from the Greek noun μέτρον , `` measure '' ) is the base unit of length in the International System of Units ( SI ) . The SI unit symbol is m . The metre is defined as the length of the path travelled by light in a vacuum in 1 / 299 792 458 seconds . </P>
the si unit of length is the meter which is defined as the length equal to
the length of the path travelled by light in a vacuum in 1 / 299 792 458 seconds