I. adjective
1.
being number one in a series
the first day of the week
Synonyms: foremost, headmost, inaugural, initial, leading
Contrasted words: final, terminal, ultimate; interjacent, intermediary, intermediate, intervenient, intervening
Antonyms: last
2.
preceding all others
succeeded at her first try
Synonyms: earliest, initial, maiden, original, pioneer, primary, prime
Related Word: early, pristine; primal, primogenial, primordial
Contrasted words: derivative, imitative, secondary
Antonyms: final
3.
exceeding all others
he was the first statesman of his era
Synonyms: arch, champion, chief, foremost, head, leading, premier, principal
Related Word: eminent, highest, preeminent, primary, prime, supreme; dominant, paramount, predominant, sovereign; main, outstanding
Contrasted words: ancillary, auxiliary, secondary, subsidiary
Antonyms: subordinate
4.
most rudimentary
had not the first chance of success
Synonyms: least, slightest, smallest
Related Word: measly, slight, slim, trifling, trivial
Contrasted words: considerable, goodly, significant, substantial, tolerable, worthwhile
II. adverb
Synonyms: firstly , initially