What does mS mean?
| Meaning | Millisiemens |
|---|---|
| Category | Science & engineering |
| Type | Symbol |
The symbol mS means millisiemens, one thousandth of a siemens. A siemens, symbol S, is a unit of electric conductance: 1 mS = 0.001 S = 1,000 microsiemens.
Case matters: mS is different from ms, the time unit millisecond. Keep the entire unit expression as well. A table labelled mS/m or mS/cm reports a per-length quantity, so dropping the denominator changes what the number describes. USGS tables use mS/m in conductivity measurements. A unit conversion alone does not determine water quality, salinity, safety or an instrument’s measurement conditions.
Meaning in context
- m
- The SI prefix milli, one thousandth.
- S
- Siemens, the conductance unit; the capital letter is significant.
Practical examples
Keep the case
- Before
4 mS is the same duration as 4 ms.
- After
4 mS is a conductance value; 4 ms is a time value.
Changing the capital letter changes the unit.
Keep the denominator
- Before
A value of 4 mS/m can be relabelled 4 mS without changing its meaning.
- After
Retain mS/m; the per-metre part belongs to the quantity being reported.
A denominator is part of the unit, not an optional caption.
Original illustrative examples, not quotations or reports of actual events.
Use mS with clarity
Why are mS, ms and mS/m different labels even when the same number appears beside them?
See all guidance
Read conductance
Preserve mS.
4 mS = 0.004 S.
Read conductivity
Keep the per-length part.
mS/m includes a denominator absent from mS.
Interpret a measurement
Keep the actual measurement context.
A unit label alone establishes no water-safety conclusion.
Preserve the capital S and any denominator when reading or converting the unit.
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By AcronymIndex Editorial Team · Editorial policy