Indicator may refer to:
In chemistry:
- pH indicator, a chemical detector for protons in acid-base titrations
- Redox indicator, a chemical detector for redox titrations
- Complexometric indicator, a chemical detector for metal ions in complexometric titrations
- Zeta potential, a property of interfaces in fluids for Zeta potential titration
In biology:
- Indicator (genus), a genus of birds in the honeyguide family
- Environmental indicator of environmental health (pressures, conditions and responses)
- Ecological indicator of ecosystem health (ecological processes)
In economics:
- Technical indicator, a tool used in the technical analysis of financial securities
- Economic indicator or business performance indicator
In mathematics, engineering, and industry:
- Indicator function of a subset of the domain, a concept in mathematics
- Indicator (distance amplifying instrument), any of various instruments used to accurately measure small distances, and amplify them to make them more obvious
- Indicator diagram, a graph of pressure against stroke within a piston engine
In society:
- A synonym for the turn signal of an automobile