When a body is divided along any of its radius , it gets divided into two equal halves . this is known as biradial symmetry
bi means two
radial means radius of its body
symmetry means equal halves on division
starfish - echinodermata

in radial symmetry , we cant say in how many halves the body is divided into but in biradial symmetry , the organism is surely divided only in 2 equal halves
bt yr..i found in ncert tht in radial symmetry.. body is divided in to two identical halves....
yeah ! it can be 2 equal halves in some situations and some thing else in other situaltions! anyways , aap kause class se ho ?
m speaking abt 11 th clss biology ncert text book
ooh ! hehe i am in 8th ! my answer was just a pure guess but later i confirmed it from my mother