adj. 1
First in importance, degree, or rank.
Our prime concern here is to keep the community safe.
adj. 2
First in time, order, or sequence.
Both the English and French governments established prime meridians in their capitals.
n. 1
The most active, thriving, or successful stage or period.
n. 2
The chief or best individual or part.

Related words

Phrases: prime mover prime minister prime cost prime factorization prime ministership prime of life prime contractor prime decomposition

Forms

Plural: primes → flowers, peaks, heydays, blooms…

Choose the right word

Prime, Primary or Primal?

Prime and primary may signify either first in time, or more frequently first in importance; primary has also the sense of elementary or preparatory; we speak of a prime minister, a primary school. Primal is chiefly poetic, in the sense of prime; as, the primal curse.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

main What is the main purpose of your studying English?
principal The principal called the teachers into his office.
ready I will see to it that everything is ready in time.
indivisible Islam is an indivisible part of a Muslim's life.

Popularity over time

Word	1850 → 2019	Trend
prime		steady
main		steady
principal		falling
ready		rising
indivisible		steady

Use in printed books, per decade from 1850 to 2019.

By length

3 letters: top¹
4 letters: best¹, main¹, peak¹, dawn¹, apex²
5 letters: first¹, white¹, ready², chief¹, youth¹, cream¹, prize¹, bloom¹, flush¹, prise
6 letters: choice¹, master², spring¹, select², flower², primal², heyday², zenith²
7 letters: morning², quality³, capital³, primary³, initial³, premier², blossom²
8 letters: original⁴, superior⁴, blockade², meridian⁴, pristine², primeval³
9 letters: beginning³, excellent³, principal³, primitive³
10 letters: aboriginal⁵, primordial⁴
11 letters: indivisible⁵
13 letters: efflorescence

The small number after each word is its number of syllables (apex² = 2 syllables).