蒙 (méng) is a literary adjective meaning 'sincere, honest, genuine' — it appears in classical-style phrases like 蒙厚 (honest and kind) or 蒙诚 (sincere at heart). Unlike the everyday 老实 (lǎo shi), which is used in speech for a simple, straightforward person, 蒙 is restricted to formal writing. It is also distinct from 由衷 (yóu zhōng 'heartfelt'), which describes feelings or words, not character.