- One of four offspring born in a single birth.
- A group or combination of four associated by common properties or behavior.
- A group of four notes having the time value of three notes of the same kind.
- Any combination of four objects or parts grouped, united, or acting together: as, a <em>quadruplet</em> of springs, consisting of four elliptic springs coupled together and acting as one spring. Also called <internalXref urlencoded="quartet">quartet</internalXref>.
- One of four born at a single birth.
- A bicycle for four riders.
- In <em>music</em>, same as <internalXref urlencoded="quartole">quartole</internalXref>.
- A collection or combination of four of a kind.
- Four children born in the same labor.
- A cycle for carrying four riders, so arranged that all the riders can assist in the propulsion.
- One of a group of four babies born from the same mother during the same birth.
- Sequence of four elements.
- one of four children born at the same time from the same pregnancy
- a set of four similar things considered as a unit
- the cardinal number that is the sum of three and one