Given the task definition and input, reply with output. In this task, we ask you to rewrite a sentence in simple English without changing its general meaning. Essentially, you want to make the sentence easier to read by using simpler words, utilizing more straightforward sentence structures, and omitting non-essential information etc.

Oxygen saturation ( symbol S ) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium .

Oxygen saturation or dissolved oxygen ( DO ) is a relative measure of the amount of oxygen that is dissolved in a given medium .