Bolt        Bolt has an external  thread at the lower end.

Screw Screw has no external thread except one head.

    Bolt        Bolts are always assembled with nuts.

Screw Screws are always used by itself.

    Bolt        It has uniform cross-section..

Screw It has non-uniform cross-section.

    Bolt        The threads are spiral in shape..

Screw The threads are helical in shape.

    Bolt        THoles are required for inserting the bolts.

Screw Usually, screws are inserted without any holes..

    Bolt        Always fixed at a single position and do not need to be turned.

Screw Being turned every time to be joined or to be removed.

    Bolt        Torque is applied to the nut  for fastening with the material.

Screw Torque is applied to the head.removed.

    Bolt        Bolts are larger in size..

Screw Screws are smaller than bolts.

    Bolt        It possesses a greater strength.

Screw It gives less strength than the bolt.