主に|おもにomoni[1]atamadaka (head-high)

1. adverbmainly; primarily; mostly; largely; chiefly
   彼かれの病気びょうきは主おもに精神的せいしんてきな物ものだった。↗

   His illness was mainly psychological.

• Synonym大方おおかたNeutralNeutral: the greater part, mostly, or roughly; can also mean people in general, as in 「大方の予想」. 「主に」 focuses on one item being the main one.
• Synonym主としてしゅとしてWrittenWritten/formal prose: same meaning as 「主に」 but more formal, as in 「主として学生を対象とする」. In speech, 「主に」 is the normal choice.
• Synonym多くおおくNeutralNeutral: as an adverb it means mostly or for the most part, as in 「多くは若者だ」, stressing that a numerical majority is involved.
• SynonymたいていNeutralNeutral: usually or mostly, as in 「大抵は家にいる」; it is about frequency or habit, not about which item is the main one.
• RelatedだいたいNeutralNeutral: roughly or on the whole, as in 「大体分かった」; it stresses approximation, while 「主に」 stresses which item is the main one.
• Related主おもNeutralNeutral: an adjectival-noun stem, mostly used as 「主な」 before a noun, as in 「主な原因」. 「主に」 is the adverb.
• Related概してがいしてWrittenWritten/formal prose: generally or on the whole, as in 「概して好評だ」; it sums up an overall impression rather than naming a main item.
• RelatedほとんどNeutralNeutral: almost or nearly, as in 「ほとんど終わった」; it stresses being close to complete, while 「主に」 only says what is main.
• RelatedあらかたNeutralNeutral: mostly or roughly, as in 「あらかた片付いた」 or 「あらかたの人」. 「主に」 instead points to what is primary among several things.
• Related総じてそうじてWrittenWritten/formal prose: on the whole, all in all; close to 「概して」 in use, it sums things up rather than singling out a main part.
• Antonym副にWrittenWritten/formal prose: secondarily, in a supporting role — the opposite of 「主に」. Few usage examples.
• Antonym従にWrittenWritten/formal prose: subordinately, in a secondary position — the opposite of 「主に」. Few usage examples.

Use 「主に」 to say what something mainly is or involves; in formal writing 「主として」 says the same. For 'roughly' use 「大体」, for 'almost all' 「ほとんど」, for 'usually' 「大抵」, and for 'on the whole' 「概して」 (or 「総じて」).

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 主ぬしとして、多おおくは、専もっぱら。