Can I completely use them as synonym of each other?
For the example:
People generally sleep in the night.
and
People commonly sleep in the night.
Learn English – the difference between general and common
vocabulary
vocabulary
Can I completely use them as synonym of each other?
For the example:
People generally sleep in the night.
and
People commonly sleep in the night.
Best Answer
In many contexts, generally and commonly are synonymous.
Indeed, if we look them up on thesaurus.com, we'll see that each is listed as the second synonym of the other.
The possible difference in meaning is well-indicated by each one's first synonym.
The first synonym listed for generally is broadly. That means that generally can be used to talk about how most people behave. (Or how most frogs smell, or how most bowls look, or whatever.)
You could say that people generally are born, live, and die. That's an incredible simplification of life, but it nevertheless describes the overall process. You couldn't substitute commonly there because there's no group of people who don't follow that pattern.
Commonly, on the other hand, can describe something that happens frequently (its first synonym) but which doesn't necessarily happen to most people. You could say people commonly die in car accidents. A billion or more people hop in a car without dying every day, so we can't say that people generally die in car accidents, but fatal accidents are nevertheless a normal enough occurrence that we wouldn't describe a traffic fatality as uncommon.
(There may be some semantics at play there depending on what you're trying to emphasize – for example, you may say car accidents are uncommon if you're trying to emphasize the safety of traveling by car over traveling by rocket-propelled skateboard or something – but the basic contrast between normalcy and frequency is what matters here.)