indicator

Everyday

1. An indicator is something that shows or points to what is happening or what is true, like a sign or measurement. tree →
2. On a car or bike, an indicator is a flashing light that shows which way the vehicle will turn (a «blinker» or «turn signal» in the US). tree →
3. In science, an indicator is a substance that changes colour to show whether something is an acid or an alkali. tree →

In the lessons

In science lessons, pupils use red cabbage juice or litmus paper as indicators of acids and alkalis. In road safety, look for a car's indicators but never trust them completely; cyclists use hand signals as indicators. In maths and data, an indicator is a measure that shows a trend, like temperature as an indicator of season. Phrases: litmus indicator, universal indicator, put the indicator on, a good indicator of.

Examples

• Litmus paper is an indicator that turns red in acid. tree →
• Red cabbage juice is an indicator: it changes colour in vinegar. tree →
• The car's left indicator was flashing. tree →
• Dad put his indicator on before turning right. tree →
• Dark clouds are an indicator of rain. tree →
• The fuel indicator showed the tank was nearly empty. tree →

Note

Countable: indicators («an» before the vowel). Verb: indicate. Car «indicator» is UK/Australian English; US says «turn signal» or «blinker». A car's indicator shows what the driver plans, but always check the car really is turning.