- Information that is known by most people within a particular community or in general; something that doesn't need to be cited or explained because it's widely understood.
Explanation
Origin
- Derived straightforwardly from the words common (belonging to or shared by many) and knowledge (facts, information, and skills acquired).
- The concept is fundamental in communication, law (e.g., judicial notice), and academia (distinguishing between what needs citation and what doesn't).
Synonyms & Related Expressions
Alternatives
Slang/Informal:
- Duh. (Dismissive, implies the information is extremely obvious)
- Tell me something I don't know. (Slightly sarcastic)
- Old news.
Vulgar/Emphatic (Usually expressing impatience):
- No shit. / No shit, Sherlock.
Milder:
- That's widely known.
- Most people are aware of that.
Situational Appropriateness
- Appropriate in most contexts, including formal and informal.
- However, stating that something is common knowledge can sometimes sound condescending if the listener genuinely doesn't know it. Use with care.
Misunderstanding Warnings
- Low risk of misunderstanding the phrase itself. The main risk is social – assuming something is common knowledge when it isn't for the listener, which can cause embarrassment or appear arrogant.
Examples
- It's common knowledge that the Earth revolves around the Sun.
- Everyone in the office knows about the merger; it's common knowledge by now.
- You don't need to tell me water is wet – that's common knowledge.
Dialogue
Student A: Did you know that Paris is the capital of France?
Student B: Uh, yeah. That's pretty much common knowledge.
Student A: Oh, right. Sorry.
Social Media Examples
- Tweet: Reminder: Recycling rules vary by city. What's common knowledge for recycling in NYC might be wrong for LA. #checklocalrules
- Forum Post: Is it common knowledge that applying early gives you a better chance? Or just a myth?
- Comment: Why are you explaining basic plot points? It's common knowledge for anyone who watched the show.
Response Patterns
- Agreement/Acknowledgement: Right. / Of course. / Everyone knows that.
- If disagreeing (rare for truly common knowledge): Actually, I didn't know that. / Is it really? I wasn't aware.
- Confirmation: Okay, good, just checking.
Common Follow-up Questions/Actions
After someone states something is common knowledge:
- The conversation usually moves on, assuming the fact is accepted.
- Someone might subtly check if it *is* common knowledge if they are unsure: So everyone's heard about the new policy then?
- If someone genuinely didn't know, they might ask for more information, potentially feeling slightly embarrassed.
After responding Actually, I didn't know that:
- The original speaker might be surprised (Oh, really?) and possibly explain the information or how it became widely known.
Conversation Starter
- No. Usually used to assert that a piece of information is already widely known, often mid-conversation or in response to someone stating the obvious.
Intonation
- Typically neutral, stating a fact. Stress often falls on common.
- It's COMmon knowledge.
- Can sometimes have a slightly dismissive or impatient tone if used to counter someone stating the obvious: Well, OBviously, that's COMmon knowledge.
Generation Differences
- Used and understood across all generations. What constitutes common knowledge might differ between generations (e.g., historical events vs. internet memes).
Regional Variations
- Universally understood and used in English-speaking regions.