(algebra) An exact sequence of precisely three nontrivial objects (e.g., modules).

The infinitely long binary sequence obtained by starting with 0 and successively appending the Boolean complement of the sequence obtained thus far.

The oldest surviving arrangement of the 64 hexagrams of the I Ching.

(mathematics) A cyclic sequence (of order n on a size-k alphabet A) in which every possible length-n string on A occurs exactly once as a substring (i.e. a contiguous subsequence). Such a sequence is denoted by B(k, n).

(pathology) A congenital defect in humans, characterized by micrognathia and resulting glossoptosis and breathing problems.

(biochemistry) a sequence of amino acids predicted from a sequence of nucleotides using information about codons used in a particular organism

Twin-to-twin transfusion syndrome.