That's false.

Use That's false. when you hear or read something that contradicts established facts. It works in spoken conversations, written messages, or even when you're just thinking to yourself. Imagine your friend claims penguins can fly. You'd immediately think, That's false. It's a quick, clear way to set the record straight. No need for a long explanation, just the core truth.

This phrase sits comfortably in the neutral to informal range. You can use it with friends, family, or colleagues in most everyday situations. However, in very formal settings, like a high-stakes legal deposition or a diplomatic meeting, you might opt for something softer. Think of it as the verbal equivalent of a crisp, clean handshake – firm, but not aggressive. It's not rude, but it's definitely not flowery either.

• Your sibling insists they cleaned their room. You know better. That's false.
• A news headline claims a celebrity is retiring. You just saw their new movie poster. That's false.
• Your friend tells you the Earth is flat. A classic! That's false.
• You're reviewing a colleague's report and spot a number that's clearly wrong. That's false.
• Someone on social media claims a historical event happened in the wrong year. You might comment, That's false.

Use That's false. when you are absolutely certain about the inaccuracy of a statement. It's best for correcting factual errors, not opinions. If someone says, "Vanilla ice cream is boring," that's an opinion. But if they say, "Vanilla ice cream has no sugar," and you know it does, then That's false. is perfect. It’s like a fact-checker in your pocket, ready to deploy!

Avoid That's false. when dealing with subjective opinions or beliefs. Saying "That's false" to someone's favorite color or their belief in ghosts can sound dismissive. Also, steer clear in highly sensitive situations where politeness is paramount. If someone is already upset, a blunt That's false. might just pour gasoline on the fire. Think of it as a tool: useful, but not for every job. You wouldn't use a hammer to stir your coffee, right?

• ✗ That is untruthful. → ✓ That's false. (Too formal and clunky for everyday use)
• ✗ No, you're wrong. → ✓ That's false. (More direct and focuses on the statement, not the person)
• ✗ That's a lie. → ✓ That's false. (A lie implies intent to deceive, which you might not know. False is neutral.)
• ✗ I disagree. → ✓ That's false. (I disagree can be about opinions; That's false is strictly about facts.)

• UK/Aus: That's not right. (Slightly softer, very common)
• Casual/Texting: Nope. or Nuh-uh. (Very informal, often used with a playful tone)
• Slightly Softer: I don't think that's correct. or Are you sure about that? (Less confrontational)
• More Assertive: That's incorrect. (A bit more formal, often used in writing)
• Humorous: My sources (aka Google) say otherwise. (Self-deprecating humor)

• Is That's false. rude? It can be perceived as blunt, but it's generally considered factual and direct, not inherently rude. Tone matters!
• Can I use it for opinions? No, stick to facts. It's for verifiable truths.
• Is it common in texting? Yes, though shorter versions like Nope are more frequent.
• What if I'm not 100% sure? Use softer phrases like I'm not sure that's right.