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sec·ond 1 (sĕkənd)
a. A unit of time equal to one sixtieth of a minute.
b. The time needed for a cesium-133 atom to perform 9,192,631,770 complete oscillations. See Table at measurement.
2. A brief interval of time; a moment. See Synonyms at moment.
3. Mathematics A unit of angular measure equal to one sixtieth of a minute. In this sense, also called arcsecond, second of arc.

[Middle English seconde, from Old French, from Medieval Latin (pars minūta) secunda, second (small part), feminine of Latin secundus, second, following; see SECOND2.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
sec·ond 2 (sĕkənd)
1. Coming next after the first in order, place, rank, time, or quality.
a. Repeating an initial instance: a second chance.
b. Reminiscent of one that is well known: a second George Washington; a second Waterloo.
c. Alternate; other: every second year.
3. Inferior to another; subordinate: second vice president at the bank; a leader second to none.
4. Music
a. Having a lower pitch.
b. Singing or playing a part having a lower range.
5. Having the second-highest ratio. Used of gears in a sequence.
a. The ordinal number matching the number 2 in a series.
b. One of two equal parts.
2. One that is next in order, place, time, or quality after the first.
3. often seconds An article of merchandise of inferior quality.
4. The official attendant of a contestant in a duel or boxing match.
5. Music
a. The interval between consecutive tones on the diatonic scale.
b. A tone separated by this interval from another tone.
c. A combination of two such tones in notation or in harmony.
d. The second part, instrument, or voice in a harmonized composition.
6. An utterance of endorsement, as to a parliamentary motion.
7. The transmission gear or gear ratio used to produce forward speeds higher than those of first and lower than those of third in a motor vehicle.
8. or seconds Informal A second serving of food.
9. Baseball Second base.
tr.v. sec·ond·ed, sec·ond·ing, sec·onds
a. To endorse (a motion or nomination) as a required preliminary to discussion or vote.
b. To support or promote: Her suggestion was seconded by several colleagues.
2. To attend (a duelist or a boxer) as an aide or assistant.
3. (sĭ-kŏnd) Chiefly British To transfer (a military officer, for example) temporarily.
1. In the second order, place, or rank: finished second.
2. But for one other; save one: the second highest peak.

[Middle English, from Old French, from Latin secundus; see sekw-1 in the Appendix of Indo-European roots.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.