In the past, both “sugu” and “suguni” have been handled without classifying. In this paper, it was considerd by the difference in the grammatical features(The possibilities of the replacing and the noun-modifying and the predicate sentence)
There is a semantic common point with short time until a new situation as time adverb, but only “sugu” is used as a degree adverb,
Time adverb “sugu”is possible to modify time noun and a spatial noun, but a verb is modified mainly. It can be a predicate sentence by the form “suguda”. Also, It can be coherent with a focus particle “wa” “demo”, but it can't be coherent ”mo”
Time adverb “suguni” can’t modify noun and only a verb can be modified. It can't be a predicate sentence, but the focus particles with adverbs can be concurrent.
On the other hand, a degree adverb “sugu” can modify noun by the form of “sugu+noun”, and an abstract distance noun is embodied or comes to the noun. But It isn't also accustomed with a predicate sentence. It isn't also used together with a focus particle.
The difference of the meaning Time adverb “sugu” and, “suguni” which couldn't touch this time, I'd like to make it future's problem. and for example “sugu” like＂彼女は人の言うことをすぐ信じるたちだ(she believes that a person says easily). It wasn't possible to treat this time, but such example can also come in sight, and I'd like to advance a study.