ずい

Etymology 1
. Possibly from ; compare the sense development that led to the senses “something straight; an exact direction, an immediate area” for reading.

First appears in the early 1500s.

Adverb

 * 1) straightforwardly, wholeheartedly, unreservedly, directly, immediately, all at once, in one go

Usage notes
Used with the adverbial particle.

Not to be confused with adverb.

Prefix

 * 1)  exactly that, directly or immediately that

Usage notes
Attaches to nouns or verbs.

In popular use during the late 1700s.

Etymology 2
Any of various on'yomi terms.