(computing theory) Both NP-easy and NP-hard.

Fidelity to one's lord or master; the feudal obligation by which the tenant or vassal was bound to be faithful to his lord. / The oath by which this obligation was assumed.

A port city in northern Israel, and the holiest city in the Baháʼí Faith.

(geometry) Any of a certain family of graphs related to Keller's conjecture, such that the vertices of the Keller graph of dimension n are the 4ⁿ elements (m₁,...,mₙ) where each m is 0, 1, 2, or 3,...