真面

First attested in 1803,^[1] but the derivation of the word with the Old Japanese-derived genitive particle つ (tsu) suggests that the term may be quite older.

Sources list this as a sound shift from compound 真 (ma, “real, true, straight”) +‎ つ (tsu, ancient possessive particle) +‎ 面 (mo, “face, facing”, usually read as omo).^[1][2][3][4] Considering the phonology, with the shift from medial /t͡su/ to /to/, this likely derives from ma tsu omo, with the tsu o- contracting to just to.

• (Tokyo) まとも (Heiban – )^[3][4][5]
• IPA^(key):

真面(まとも) • (matomo) -na (adnominal 真面(まとも)な (matomo na), adverbial 真面(まとも)に (matomo ni))

1. direct, straight, frontwards

   Synonym: 正面 (shōmen)

2. honest, proper, upright, correct, appropriate

   Synonyms: 正直 (shōjiki, “honest”), 正しい (tadashii, “proper, upright”)

   まともな食事(しょくじ)をしていない

   matomo na shokuji o shite inai

   not eating proper meals → eating badly

Compound of 真 (ma, “real, true; straight”) +‎ 表 (omote, “front side, front facing”).^[1][3]

First attested in 1896.^[1]

Not included in some dictionaries.^[4][5]

• (Tokyo) まおもて (Nakadaka – )^[3]
• IPA^(key):

真(ま)面(おもて) • (maomote) 

1. (uncommon) the direct front of something

   Synonyms: 正面 (shōmen), 真向い (mamukai)

Alternative spelling for 真秀 (maho, “sufficient, complete, in order”).^[1]