本当

Etymology
First appears in the late in a text from 1770. The clipped reading with the shorter second vowel is regarded as a simple shift from original reading,  and this first appears in a text from 1886.

Adjective

 * 1)  true, proper, real

Usage notes

 * The form for the attributive is nonstandard and rare.  is used instead.  This usage pattern was already apparent by at least 1785.

Noun

 * 1)  truth, reality

Usage notes

 * Usually pronounced as instead of, especially by young ladies.