# Definition of inertial in English:

## inertial

Physics
• 1Relating to or arising from inertia.

‘high-speed centrifuges generate large inertial forces’
‘the inertial load on the motor’
• ‘The interesting thing is that, physically, no difference has been found between gravitational and inertial mass.’
• ‘In Newton's theory, all three of these masses - the inertial mass, the active and passive gravitational masses - are equivalent.’
• ‘If its axis were to be suddenly shifted from its normal inclination, inertial forces produced in such a change would literally tear the earth apart.’
• ‘Einstein warmed to the idea that the gravitational field of the rest of the Universe might explain centrifugal and other inertial forces resulting from acceleration.’
• ‘Another way of understanding the situation is to remember the equivalence Einstein explained between gravitational and inertial forces.’
1. 1.1 (of navigation or guidance) depending on internal instruments which measure a craft's acceleration and compare the calculated position with stored data.
• ‘The aircraft's navigation system includes an integrated inertial navigation and global positioning INS / GPS system.’
• ‘The aircraft uses a Honeywell inertial navigation system.’
• ‘Inside is a guidance control unit with inertial navigation and global positioning systems.’
• ‘The missile has new GPS / INS (global positioning / inertial navigation) guidance and kinetic warhead.’
• ‘A rocket's inertial guidance system measures acceleration along three principal directions.’
2. 1.2 (of a frame of reference) in which bodies continue at rest or in uniform straight motion unless acted on by a force.
‘the laws of physics take the same form in all inertial frames’
• ‘The rest-mass of a body is the inertial mass of that body when it is at rest relative to an inertial frame.’
• ‘Mach had stated a principle that local inertial frames of reference were determined by the large scale distribution of mass in the universe.’
• ‘Photons, according to the special theory of relativity, move in vacuum with the same speed in all inertial frames of reference.’
• ‘A reference frame in which star motion is ignored and the stars are assumed to be at rest is approximately an inertial reference frame and is often adequate for many purposes.’
• ‘Simple laws apply to constant motion in a straight line (an inertial frame of reference).’

/ɪˈnəːʃ(ə)l/