perfect elasticity and unitary elasticity

what is perfect/inperfect elasticity/inelasticity? and unitary elasticity? Thanks.

unitary elasticity is when a change in price % creates same change % in the demand perfect elasticity means that a change in price will reduce demand to 0 perfect inelasticity means that no matter how much you change prices demand will not change. hope i got this right

perfectly elastic is a horizontal line… prefectly INelastic is a vertical line… as long as you know that, the rest is easy…its just a matter of reading/interpreting the graph…