236
Chapter 7.
9.54.
References to meridian in statements of time are abbreviated as follows:
- 10 a.m. (not 10:00 a.m.)
- 2:30 p.m.
- 12 p.m. (12 noon)
- 12 a.m. (12 midnight)
9.55.
The word o'clock is not used with abbreviations of time.
not 10 o'clock p.m.
9.56.
Metric unit letter symbols are set lowercase roman unless the unit name has been derived from a proper name, in which case the first letter of the symbol is capitalized (for example Pa for pascal and W for watt) . The exception is the letter l. for liter. The same form is used for singular and plural. The preferred symbol for cubic centimeter is cm³; use cc only when requested.
A space is used between a figure and a unit symbol except in the case of the symbols for degree, minute, and second of plane angle.
- 3 m
- 45 mm
- 25 ºC
- but 33°15'21"
| Prefixes for multiples and submultiples | Metric units | ||||
| E | exa (1018) | d | deci (10-1) | m | meter (for length) |
| P | peta (1015) | c | centi (10-2) | g | gram (for weight or mass) |
| T | tera (1012) | m | milli (10-3) | l. | liter (for capacity) |
| G | giga (109) | μ | micro (10-6) | ||
| M | mega (106) | n | nano (10-9) | ||
| k | kilo (103) | p | pico (10-12) | ||
| h | hecto (102) | f | femto (10-15) | ||
| da | deka (10) | a | atto (10-18) | ||
| Length | Area | Volume | |||
| km | kilometer | km² | square kilometer | km³ | cubic kilometer |
| hm | hectometer | hm² | square hectometer | hm³ | cubic hectometer |
| dam | decameter | dam² | square decameter | dam³ | cubic dekameter |
| m | meter | m² | square meter | m³ | cubic meter |
| dm | decimeter | dm² | square decimeter | dm³ | cubic decimeter |
| cm | centimeter | cm² | square centimeter | cm³ | cubic centimeter |
| mm | millimeter | mm² | square millimeter | mm³ | cubic millimeter |
