<p>ScD in the US is not too common, but when it’s awarded as an earned (e.g. not honorary) degree it’s usually equal to a PhD.</p>
<p>However, at the ancient universities (e.g. Cambridge) the PhD is the only doctorate that one earns through research and coursework. Doctor of Science, Doctor of Law, Doctor of Letters, Doctor of Divinity and Doctor of Music are all considered ‘higher doctorates’ and are only awarded to someone much later in their career (often as an honorary degree… they don’t give out honorary PhDs). </p>
<p>In the US there is also the Doctor of Medicine (MD) and Juris Doctor (JD) degrees, neither of which are strictly speaking doctorates. However, by convention medical doctors (although not lawyers) are still called “Dr.” Instead, lawyers in the US have laid claim to the title Esq. after their name… although it’s a totally incorrect usage of the title (any gentleman is titled Esq. unless they have another title) it has stuck here in the US.</p>