a.m.

• a. m., am, AM, A. M., A.M.
• a, A (chiefly American)

Abbreviation of ante meridiem ("before noon").

• Audio (US):

  (file)

a.m. (not comparable)

1. (used after the hour) In the 12-hour period from midnight to noon (the first half of the day) when using the 12-hour clock.
   • 1967, United States Travel Service, Plant Tours for International Visitors to the United States, page 49:

     Greenfield Monday thru Friday, 9 to 12 a.m.

   • 2001, Customs Service effects of proposed legislation on officers' pay, United States General Accounting Office, page 45:

     One of the most common night shifts is the 12 a.m.-to-8 a.m. shift.

   • 2007, Khurana Rohit, Number Game 4, page 144:

     We never say 12 a.m. or 12 p.m. It's either 12 midnight or 12 noon, respectively.

   • 2009, Robert Bill, Medical Mathematics and Dosage Calculations for Veterinary Professionals, page 348:

     The 12-hour clock uses A.M. for the morning hours of midnight (12:00 A.M.) to almost noon (11:59 A.M.) and the P.M. designation for the hours from noon (12:00 P.M.) to almost midnight (11:59 PM).

   • 2015, Arhlene A. Flowers, Global Writing for Public Relations, page 141:

     The 12-hour clock, which is used in the U.S., Canada, and a few other countries, divides time into two cycles: a.m. (ante meridiem, Latin for before midday) from midnight, 12 a.m., to 11:59 a.m.; and p.m. (post meridiem, Latin for after midday) from noon, 12 p.m., to 11:59 p.m.

   • 2021, Jukka Heinonen, Ortzi Akizu-Gardoki, Sanna Ala-Mantila, Energy Efficient Cities of Today and Tomorrow, page 196:

     The following daylight peaks are identified around lunchtime, from 12 am to 1 pm, while for weekend days, the curve show several daylight peaks from 7 am to late lunchtime, around 1 pm.

• As seen in the quotes above, "12 a.m." has sometimes been used to mean either noon or midnight. However, the National Institute of Standards and Technology contends that those uses are incorrect.
• Some argue that it should not be used in English as a noun meaning "morning" on account of the fact that it is an abbreviation for a Latin adverbial phrase.

• in the forenoon

• p.m.
• in the afternoon

a.m. (not comparable)

1. Initialism of ad modum.

• -ma-, M&A, M.A., MA, Ma, ma

• Audio:

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a.m.

1. Abbreviation of amica manu.: (delivered) by the hand of a friend (put on an address)
2. Abbreviation of ante meridiem.: a.m., in the forenoon

• 's morgens
• 's ochtends

a.m. (not comparable)

1. a.m. (before noon)/(antes do meio dia) (Portuguese language)