Synonyms for First and foremost:

• adv.

  •mainly (adverb)
  • largely,
  • in general,
  • predominantly,
  • in the main,
  • mostly,
  • substantially,
  • essentially,
  • generally,
  • to the greatest extent,
  • usually,
  • chiefly,
  • most of all,
  • mainly,
  • overall,
  • above all,
  • on the whole.
  •principally (adverb)
  • basically,
  • peculiarly,
  • Prevalently,
  • eminently,
  • vitally,
  • cardinally,
  • Prevailingly,
  • particularly,
  • to a great degree,
  • universally,
  • preeminently,
  • superlatively,
  • especially,
  • for the most part,
  • importantly,
  • materially,
  • before anything else,
  • supremely,
  • fundamentally,
  • dominantly,
  • notably.

• adv

  •in the beginning (adverb)
  • primarily.
  •Other relevant words: (adverb)
  • at the start,
  • at first,
  • primitively,
  • from the start,
  • in first place,
  • in the first place.
  •principally (adverb)
  • pre-eminently.

• n.

  •first and foremost (noun)
  • most importantly.
  •Other relevant words: (noun)
  • firstly.

• Other synonyms:

  •chiefly
  • principally.
  •Other relevant words:
  • importance,
  • preference,
  • precession,
  • priority,
  • Previousness,
  • dominance,
  • precedence,
  • precedency,
  • order,
  • way,
  • state,
  • lead,
  • predominance,
  • prevalence,
  • prominence,
  • mode,
  • supremacy,
  • superiority,
  • antecedence,
  • preeminence,
  • greatness,
  • Prevenience,
  • significance,
  • primacy,
  • manner.
  •Other relevant words (noun):
  • chief,
  • first of all,
  • before everything,
  • originally,
  • first off,
  • initially,
  • first,
  • ab ovo,
  • first thing.

Antonyms for First and foremost:

• adv.

  • mainly
    secondarily.
  • primarily
    finally.
  • principally
    trivially.