common = rare の反対語
general = specific の反対語

つまり、
common = ざらにある、よく見かけられる
general = 限定されていない、広い意味で


【Example: In Korea.】
Do you see that lady? The exact perm she has is really common in this country. (generalとは言わない)

【Example】
A: Help! There's a wild animal in the parking lot!
B: You're being too general. Is it a dangerous animal? (too commonとは言わない)

common は、よくある、よく使われる、ありがちな
general は、一般的,

日本だとcommon も一般的と訳す事が多いですが、
common, commonly は (general, generally より) casual, informal に使います。

That’s a common idea. よくある考えです。ありがちな
That’s the general idea. 一般的な考えです。

例えば、
People generally sleep at night. 人は、一般的に夜に眠ります。
People commonly sleep at night. は、人はよく夜に眠ります。という意味になり、英語でも不自然です。

@iquit I like that explanation.

I have to say, though, 一般的な考え actually means something closer to "a common idea" because it means an idea shared by the general public, not an idea free of specificity.

That's probably where the confusion happens for Japanese people.

@us4gi Your clear explanation helped me understand these words, thank you!　You are right. I often get confused about the use of these two words because I think "一般的な考え = common idea"!

@iquit You're so good at making things easily understandable. "common idea" を "ありがちな" と訳すのが腑に落ちました。Thank you so much!

Common means it's found in a lot of places or is used often. General is similar to common but it means that it is normal or broad.

For example:

It's common to see birds in the Spring.

I took general biology course in college.

common- means most often ("The most common thing people order from this restaurant is the fish. It's delicious and everyone wants to try it.")
general- 1) means not exact, but close ("I didn't quite understand what my math teacher tought us today, but I'm confident I have enough of a general idea to pass the quiz tomorrow." or 2) generally- meaning in most cases/ usually ("I generally come home from work at 6:15")

common is closer to daily life.
e.g. common knowledge.
general can be more formally used in writing.
e.g. general awareness.

Common = About rarity, not being special
General = The average/majority. Think of a trend line in a data set. (Like in the attached image)

They’re usually interchangeable.

Examples:
Most shirts do not have frills. Frilled shirts are not common.

In general, most shirts do not have frills.

Voters generally voted for the candidate who supported their side of the dumbbell debate. (But some decided based off of other issues)

You would say “general(ly)” as in
Generally, in America people are nice
You would say “common(ly)”
It is common for Americans to eat dinner early

It really depends on context. Both are used in different sentences.

@wenhuoz
General means universal it means that regardless of what topic or scenario the rules are the same.
Common means same or similar it means that regardless of situations rules are similar but may have slight difference.

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.

http://www.thesaurus.com/browse/generally
http://www.thesaurus.com/browse/commonly
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.)

@zohaibAnsar soooo thank you!!
No one answered my question.
Thank you for writing it in detail and sincerity. You make me want to learn English more.😊😊

General is reffering to everyone while common means something by two or more people, group or things.

Common means you can find/see it everywhere.
"This shirt design is so common."

General means overall of a something. It is usually unclear.
"In general, ten people die every second."