deductive

UK/dɪˈdʌktɪv/US/dɪˈdʌktɪv/

adjectiveC2Very rare — outside the 30,000 commonest English words, so you will meet it in writing rather than in speech — deduct sits at #8,039neutraltechnical · an editor’s judgement

Deductive means reasoning downward from general rules to the particular case. If all of these are true, then this must be too.

It is one half of a famous pair, since deductive reasoning moves from the general to the specific and inductive reasoning moves the other way, building a general rule from particular observations. Deduction is watertight when the premises are true and induction never quite is. Sherlock Holmes is famous for deduction and almost everything he actually does is induction, which purists have complained about for a century.

Definitions of deductive

1adjectivedeductiveReasoning from general principles to a particular conclusion.C2
“The proof is entirely deductive and depends on the first assumption.”

Where it comes from

Proto-Indo-European
*dewk-
Latin
deductus
English
deduct
English, today
deductive

Built from

deduco · Latin — lead from

From deduct + -ive. deduct Borrowed from Latin deductus, perfect passive participle of verb deduco (“lead from”).

Etymology from Wiktionary, CC BY-SA

Practised in A Man Called Ove

First appears in chapter 36 of A Man Called Ove.

Practise this word

deductive in the wild

In logic, soundness can refer to either a property of arguments or a property of formal deductive systems.
Soundness
The former is more relevant for introductory deductive reasoning contexts and the latter arises in metalogic and mathematical logic.
Soundness
One approach defines deduction in terms of the intentions of the author: they have to intend for the premises to offer deductive support to the conclusion.
Deductive reasoning
Invalid deductive arguments, which do not follow a rule of inference, are called formal fallacies.
Deductive reasoning
Among its most common forms are: Causal explanation Deductive-nomological explanation, involves subsuming the explanandum under a generalization from which it may be derived in a deductive argument.
Explanation

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From Wikipedia, CC BY-SA 4.0. These sentences were written by other people about their own subjects; they are here to show the word at work, not as anybody’s opinion.

Related words

the deduco family

deduct deduce

deductive — used too rare to measure · point at the bar for the others

deduction

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