The official name of Wales prior to England's union with Wales in 1542. / In general use, the full name of Wales.

plural of principal investigator

(sciences) lead researcher on a grant-funded project

plural of principal ultrafilter

plural of principal ideal

(grammar, usually in the plural) Any of the forms of a word which contain its stem(s) in the simplest form, or such a form that, when taken with all the other principal parts, allows the entire paradigm to be derived.

plural of principal part

(algebra) An integral domain in which every ideal is a principal ideal.

(physics) The quantum number (of an atomic orbital) that specifies the energy of an electron in an atom and, hence, which shell it occupies

(algebra, ring theory) A commutative ring in which every ideal is a principal ideal.