valid

Everyday

1. Valid means officially acceptable and able to be used, for example because it has not run out: «a valid ticket», «a valid passport». tree →
2. Valid means sensible and based on good reasons: «a valid point», «a valid excuse». tree →
3. In maths and science a valid test or answer follows the rules correctly: «a valid conclusion». tree →

In the lessons

In science lessons a «valid» or fair test changes only one variable, so the results really answer the question. In maths and reasoning, a valid answer must fit all the conditions. In everyday life tickets, coupons and passports are valid until a certain time. In discussions, teachers say «that's a valid point» to respect an idea. Phrases: «valid for», «valid until», «a valid reason», «a valid point».

Examples

• Your bus ticket is valid for one day. tree →
• That's a valid point. tree →
• Is my passport still valid? tree →
• Forgetting isn't a valid excuse. tree →
• To make the test valid, change only one thing. tree →
• The coupon is no longer valid. tree →
• Check your answer is valid in the problem. tree →

Note

Opposite: invalid. Noun: validity. Verb: validate. In maths, an answer like «3.5 children» is not valid when counting people.