Reliable means you can count on it, every single time. The car that starts on a frosty morning, the friend who turns up when they said they would, the printer that never jams.
You use reliable for people and for things: a reliable colleague, a reliable washing machine, a reliable train service. It stretches to information too — a reliable source, a reliable witness, reliable data — where it means the thing is worth believing. The noun is reliability, the adverb is reliably ('reliably informed'), and behind both sits the verb rely, which takes ON: you rely on someone reliable. Watch the near-twin: reliant means depending on something, so a village reliant on tourism is not the same thing as a village with reliable tourism. And the opposite carries real weight — calling a person unreliable is a serious complaint, not a mild one.
1adjectivereliableAble to be trusted to do what is needed, every time.
“We need a reliable van, not a cheap one.”
synonyms: dependable, trustworthy
2adjectivecredibleOf information or its source: likely to be correct, and safe to act on.
“Two reliable sources confirmed the numbers before the paper ran the story.”
Also accepted in games: dependable, trustworthy
From rely + -able.
Etymology from Wiktionary, CC BY-SA