Disjunct

A disjunct is an adverbial phrase with information that is not considered essential to the sentence. It expresses the speaker's attitude towards the sentence. The disjunct refers to any part of the sentence which is not fully integrated into the clausal structure of the sentence. The disjunct usually appears peripherally, at the beginning or end of the sentence.

Here are examples of disjuncts:

Fortunately for you, I can give you an extension.
Frankly, the whole presentation needs revision.
Honestly, I didn't see anything.
Luckily, she arrived on time.
Unfortunately, by the time he arrived, most of them had already left.

In certain cases, the same word or phrase can be interpreted as an adjunct or disjunct.

They seriously worked in an underground diamond mine in South Africa.

The disjunct meaning is that the speaker is serious when he/she says that they worked in an underground diamond mine. The adjunct meaning is that they worked in a serious manner while in an underground diamond mine. With the disjunct meaning seriously is a sentence adverb and with the adjunct meaning, it is an adverb of manner.

Disjuncts are adverbial phrases which are not an essential part of the sentence. They usually appear peripherally. In certain cases, the adverbial can be interpreted as either an adjunct or a disjunct.