|1.||See economic indicator something that provides an indication, esp of trends|
|2.||a device to attract attention, such as the pointer of a gauge or a warning lamp|
|3.||an instrument that displays certain operating conditions in a machine, such as a gauge showing temperature, speed, pressure, etc|
|4.||a. a device that records or registers something, such as the movements of a lift, or that shows information, such as arrival and departure times of trains|
|b. (as modifier): indicator light|
|5.||Also called: blinker a device for indicating that a motor vehicle is about to turn left or right, esp two pairs of lights that flash when operated or a pair of trafficators|
|6.||Also called: dial gauge a delicate measuring instrument used to determine small differences in the height of mechanical components. It consists of a spring-loaded plunger that operates a pointer moving over a circular scale|
|a. a substance used in titrations to indicate the completion of a chemical reaction, usually by a change of colour|
|b. a substance, such as litmus, that indicates the presence of an acid or alkali|
|8.||ecology Also called: indicator species|
|a. a plant or animal species that thrives only under particular environmental conditions and therefore indicates these conditions where it is found|
|b. a species of plant or animal whose well-being confirms the well-being of other species in the area|
indicator in·di·ca·tor (ĭn'dĭ-kā'tər)
One that indicates, especially a pointer or an index.
An instrument used to monitor the operation or condition of an engine, an electrical network, or another physical system; a meter or gauge.
The needle, dial, or other registering device on such an instrument.
Any of various substances, such as litmus or phenolphthalein, that indicate the presence, absence, or concentration of another substance or the degree of reaction between substances by means of a characteristic change, especially in color.
|indicator (ĭn'dĭ-kā'tər) Pronunciation Key
A chemical compound that changes color and structure when exposed to certain conditions and is therefore useful for chemical tests. Litmus, for example, is an indicator that becomes red in the presence of acids and blue in the presence of bases.
any substance that gives a visible sign, usually by a colour change, of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution. An example is the substance called methyl yellow, which imparts a yellow colour to an alkaline solution. If acid is slowly added, the solution remains yellow until all the alkali has been neutralized, whereupon the colour suddenly changes to red
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