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Meaning of deadly
The primary meaning of "deadly" is causing or capable of causing death.
Etymology of deadly
The word "deadly" has its roots in Old English "dēaþlīc" meaning "death-like" or "causing death", derived from "dēaþ" meaning "death" and the suffix "-līc" forming an adjective
 Historically, the term has been used to describe things that can cause death, such as poisonous substances, diseases, or actions that can lead to fatal consequences
Synonyms
                                                lethal
                                                                        fatal
                                                                        mortal
                                                                        poisonous
                                                                        toxic
                                                                        venomous
                                                                        hazardous
                                                                        perilous
                                                                        dangerous
                                                                        risky
                                                                        threatening
                                                                        menacing
                                                                        harmful
                                                                        destructive
                                                                        calamitous
                                                                        disastrous
                                                                        catastrophic
                                                                        devastating
                                                                        murderous
                                                                        homicidal
                                                                        suicidal
                                                                        killer
                                                                        deathly
                                                                        baneful
                                                                        noxious
                                                                        malignant
                                                                        virulent
                                                                        pestilent
                                                                        infectious
                                                                        contagious
                                                                        deadly
                                                                        savage
                                                                        brutal
                                                                        ferocious
                                                                        vicious
                                                                        cruel
                                                                        ruthless
                                                                        merciless
                                                                        pitiless
                                                                        inhuman
                                                                        barbarous
                                                                        inhumane
                                                                        heinous
                                                                        atrocious
                                                                        abhorrent
                                                                        detestable
                                                                        odious
                                                                        repugnant
                                                                        abominable
                                                                        loathsome
                                                                        hateful
                                                                        execrable
                                                                        diabolical
                                                                        fiendish
                                                                        hellish
                                                                        infernal
                                                                        diabolic
                                                                        satanic
                                                                        demonic
                                                                        devilish
                                                            
            Definitions
- Causing or capable of causing death
 - Extremely dangerous or harmful
 - Giving an impression of extreme competence or skill
 
Usage Examples
- The new disease is deadly and has already claimed several lives
 - The snake's venom is deadly and can kill a person within hours
 - The driver's reckless behavior was deadly and put everyone on the road at risk
 
Antonyms
                                                harmless
                                                                        safe
                                                                        non-toxic
                                                                        benign
                                                                        innocuous
                                                                        mild
                                                                        moderate
                                                                        slight
                                                                        minor
                                                                        negligible
                                                                        insignificant
                                                                        trivial
                                                                        non-lethal
                                                                        survivable
                                                                        recoverable
                                                                        reversible
                                                                        curable
                                                                        treatable
                                                                        palliative
                                                                        mitigable
                                                                        containable
                                                                        harmless
                                                                        risk-free
                                                                        secure
                                                                        protected
                                                                        sheltered
                                                                        guarded
                                                                        defended
                                                                        impregnable
                                                                        invulnerable
                                                                        inviolable
                                                                        unassailable
                                                                        unattackable
                                                                        impervious
                                                                        resistant
                                                                        immune