sphere (ROUND OBJECT)phoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhonetic PhoneticPhoneticPhoneticPhoneticPhoneticphonetic noun [C] 
an object shaped like a round ball 
Every point on the surface of a sphere is at an equal distance from its centre.
Doctors have replaced the top of his hip bone with a metal sphere.

spherical phoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhonetic PhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticphonetic adjective 
The Earth is not perfectly spherical (=round like a ball).

spheroid phoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhonetic PhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticphonetic noun [C] SPECIALIZED 
A spheroid is a solid object that is almost spherical. 
The Earth is a spheroid.
( Cambridge International Dictionary of English )