A tuplet of four notes.
One of a group of four, particularly one of four babies born from the same mother during the same birth.
A sequence of four elements.
A cycle for carrying four riders, arranged so that all the riders can assist in the propulsion.
A word of four syllables.
A type of four-dimensional hypercomplex number consisting of a real part and three imaginary parts (real multiples of distinct, independent square roots of −1 denoted by i, j and k); commonly used in vector mathematics and as an alternative to matrix algebra in calculating the rotation of three-dimensional objects.
A group or set of four people or things.