The definition of space (synonym: vacuum, nothing, spacetime, field, region, continuum, emptiness):
space: that which lacks shape.
Space lacks the property of objects, namely, shape. In physics space cannot be qualified with an adjective in a sentence. Space refers to a concept and all concepts lack shape. In this definition space does not mean a 'lack of something' or 'empty' since that suggests matter is missing from the region of the universe which is absurd.
Newton failed to conceive of those fundamental-continuous-invisible-physical objects that mediate gravitational attraction between physical objects. Instead he gave his readers this notion called 'absolute space' along with a lot of math. Absolute is an adjective inherited from the Greeks that means 'without relation to anything'. It is a self-refuting concept since all concepts are necessarily relations by definition. 'Absolute' is a linguistic contradiction, an oxymoron for the purposes of physics. In addition an adjective cannot qualify a concept: absolute cannot modify space. In physics adjectives cannot qualify concepts. Concepts reference static or dynamic relations between two or more objects picked out by the brain of the conceiver.
Einstein inherited Newton's 'absolute space' and converted this notion into 'spacetime'. Einstein also failed to conceive of a rational physical object that mediates gravitational attraction. He gave us a few good insights and some pretty math. Now disciples of Einstein think that spacetime is that which has shape, in other words an object of physics. And, for them, this 'spacetime' mediates gravitational attraction.
Many a physicist has mistaken the concept SPACE, that which lacks shape, for the supposed objective physical mediator of light and gravity. We cannot see that which mediates light and gravity thus an assumption of this physical mediator has become a great game spanning centuries. Instead of giving us a rational supposition of an object that may mediate light and gravity, many a physicist cloaks their failure in endless esoteric math and rhetoric about infinity, fields, universes, curvature, nothing, blah blah blah.