1. First or highest in rank or importance; main: Our prime consideration is for the children's safety. See Synonyms at chief. See Usage Note at perfect.
a. Highest in quality; excellent: prime real estate.
b. Being the most desired or suitable example of something: a prime candidate for the study.
3. Of or relating to the USDA highest grade of beef, having abundant marbling and usually only sold at restaurants.
4. First or early in time, order, or sequence: the prime action of the drug.
5. Mathematics Of, relating to, or being a prime number.
a. The period of greatest physical and mental robustness: athletes in the prime of their lives.
b. The period of best performance or peak activity: This car is definitely past its prime. See Synonyms at bloom1.
2. Mathematics A prime number.
3. The prime rate.
4. A mark (′) appended above and to the right of a character, especially:
a. One used to distinguish different values of the same variable in a mathematical expression.
b. One used to represent a unit of measurement, such as feet or minutes in latitude and longitude.
5. also Prime Ecclesiastical
a. The second of the seven canonical hours. No longer in liturgical use.
b. The time appointed for this service, the first hour of the day or 6 AM.
6. Linguistics See primitive.
7. The first position of thrust and parry in fencing.
v. primed, prim·ing, primes
1. To make ready; prepare: guard dogs primed for attack.
2. To prepare (a gun or mine) for firing by inserting a charge of gunpowder or a primer.
3. To prepare for operation, as by pouring water into a pump or gasoline into a carburetor.
4. To prepare (a surface) for painting by covering with size, primer, or an undercoat.
5. To inform or instruct beforehand; coach.
To become prepared for future action or operation.
prime the pump Informal
To encourage the growth or action of something.
[Middle English, first in occurrence, from Old French, feminine of prin, from Latin prīmus; see per1 in the Appendix of Indo-European roots. Noun, sense 5, from Middle English, from Old English prīm, from Late Latin prīma (hōra), first (hour), from Latin, feminine of prīmus.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. 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:
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.