Logic
Etymology
From Greek "logike techne" (the art of reasoning), from "logos" (word, speech, reason, account) — the same "logos" that ends countless -ology words. Logic began as the discipline of reasoned discourse and became the formal study of inference itself.
noun · /LOJ-ik/
The study of correct reasoning — how conclusions do or don’t follow from premises.
What it names
Use it for the rules that govern valid inference, the machinery that decides whether an argument holds together regardless of its subject.
Example
The conclusion may be true, but the logic connecting it to his premises simply doesn’t work.
Related idea
The surprising thing logic teaches is that it cares about form, not content: it checks whether a conclusion follows, not whether the premises are true. That’s why an argument can be flawless in logic and false in fact — see valid versus sound.