Alkyne
Definition
Hydrocarbons with at least one carbon-carbon triple bond: the most unsaturated family, including acetylene used in welding torches.
Technical definition
Alkynes are unsaturated hydrocarbons containing at least one C-C triple bond (general formula CnH2n-2 for one triple bond). They are linear at the triple bond and undergo addition reactions, with terminal alkynes being weakly acidic.
Example
Acetylene (C2H2) burns at over 3000 C in oxy-fuel welding torches: the hottest common flame.
Common confusion
Triple bonds are shorter and stronger overall than double bonds, but still reactive. A stronger bond does not mean less reactive, since the two pi bonds are exposed to attack.