explosive
Word family
Synonym discussion
Sense: adjective/1
All three words describe something that can change dangerously, but they highlight different risks. 'Explosive' (the headword here) specifically means something can burst apart violently — think of a gas canister or bomb. 'Volatile' is more technical and broad: a volatile chemical turns into gas easily at room temperature, which makes it a fire or explosion risk, but the word also describes unstable political situations (a volatile region). 'Combustible' is narrower — it means something can catch fire and burn, but not necessarily explode (wood is combustible but not explosive). 'Unstable' is the most general: an unstable chemical compound can react unpredictably, and an unstable structure can collapse. In everyday contexts, 'explosive' (adj/1) is the strongest word, implying violent force; 'volatile' suggests risk that could go either way; 'combustible' focuses on fire risk; and 'unstable' covers any kind of dangerous unpredictability. For example, you would call dynamite 'explosive', petrol vapour 'volatile', a pile of dry leaves 'combustible', and a shaking ladder 'unstable'.
Common collocations
Etymology
The word 'explosive' comes from the Latin verb 'explodere', which originally meant 'to drive an actor off the stage by clapping and hissing'. It was formed from 'ex-' (out) and 'plaudere' (to clap). In the 1500s, the meaning shifted to describe a sudden, violent burst of sound or force under pressure. By the 1600s, the adjective 'explosive' was used for gunpowder and similar substances. The modern scientific sense — describing a substance that releases gas and heat at extreme speed — developed during the 1800s as chemistry and mining advanced.