Seconds Abbreviations: s, sec, or secs?
For scientific and technical unit notation, the accepted symbol for second is lowercase “s.” NIST states that unit symbols are not abbreviations, are not pluralized, and do not take a period; it also identifies “sec” as impermissible for the SI unit second.
Use lowercase “s” as the standard symbol for second: “1 s,” “30 s.” In SI-style measurement writing, avoid “sec,” “secs,” and plural “ss.”
Key details
Important caveats
Sec Boundary
In SI-style notation, use “s” rather than “sec”; NIST explicitly treats “sec” as impermissible for the unit symbol.
Further guidance
Pluralization
Keep the symbol unchanged for plural quantities: “30 s,” not “30 secs.”
Standard Form
Write lowercase “s” after the value: “10 s.”
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Writing with SI (Metric System) Units (opens in a new tab)National Institute of Standards and Technology · NIST unit-symbol rules, including no plural s on symbols
- SP 330 Section 5 — Rules and Style Conventions for Printing and Using Units (opens in a new tab)National Institute of Standards and Technology · Authoritative SI style rules: unit symbols are not pluralized or followed by periods, and sec is not the permissible symbol for second