What is domain authority (DA) ?

[nancy07]

Domain Authority is a score (on a 100-point scale) developed by Moz that predicts how well a website will rank on search engines. Use Domain Authority when comparing one site to another or tracking the “strength” of your website over time. We calculate this metric by combining all of our other link metrics—linking root domains, a number of total links, MozRank, MozTrust, etc.—into a single score.

[davidweb09]

Domain authority can be measured on the basis of quality & age of domain used for business.