Your English: Collocations: deadly, lethal, fatal

The adjectives deadly, lethal and fatal all have broadly the same meaning. Deadly means ‘able or likely to kill people’, lethal is defined as ‘very dangerous and able to kill you’ and fatal has the meaning of ‘causing someone to die’.

There are a couple of cases where collocations including these adjectives overlap, e.g. a disease can be deadly, lethal or fatal, although a specific disease can only be fatal, e.g.  ‘He suffered a fatal heart attack’ or ‘The infection proved fatal’. Weapons can be both lethal and deadly but not fatal.

Nouns that specifically collocate with deadly include poison, virus and threat, as in ‘In the wrong hands, spent nuclear material could pose a deadly threat’, while nouns that collocate with lethal include dose, injection and effect, as in ‘In some US states, people are executed by lethal injection’.

Lethal is also used with words that specifically indicate a mixture that can cause death, as in ‘She was found dead in her kitchen, having taken a lethal cocktail of alcohol and weedkiller’ and ‘John was a heavy drug user and an alcoholic – a lethal combination’.

Fatal is specifically used with events that cause death such as accident, crash, collision and fall, as in ‘He met with a fatal accident at the colliery yesterday’. It is also used in situations where someone is hurt, such as attack, blow, injury, shot and wound, and in situations involving a very costly mistake with the words mistake, error and blunder, as in ‘Never underestimate him because you will be making a fatal error’.