Dotted notes and their equivalent durations. The curved lines, called ties, add the note values together.

In Western musical notation, a dotted note is a note with a small dot written after it. In modern practice, the first dot increases the duration of the basic note by half of its original value. This means that a dotted note is equivalent to writing the basic note tied to a note of half the value – for instance, a dotted half note is equivalent to a half note tied to a quarter note. Subsequent dots add progressively halved value, as shown in the example to the right. Though theoretically possible, a note with more than three dots is highly uncommon; only quadruple dots have been attested.

The use of a dot for augmentation of a note dates back at least to the 10th century, although the exact amount of augmentation is disputed; see Neume.

A rhythm using longer notes alternating with shorter notes (whether notated with dots or not) is sometimes called a dotted rhythm. Historical examples of music performance styles using dotted rhythms include notes inégales and swing. The precise performance of dotted rhythms can be a complex issue. Even in notation that includes dots, their performed values may be longer than the dot mathematically indicates, a practice known as over-dotting.

https://en.wikipedia.org/wiki/Dotted_note

The Bach-Werke-Verzeichnis (BWV; Bach works catalogue) is a catalogue of compositions by Johann Sebastian Bach. It was first published in 1950, edited by Wolfgang Schmieder. The catalogue’s second edition appeared in 1990. An abbreviated version of that second edition, known as BWV^2a, was published in 1998.

1126 compositions were assigned a BWV number in the 20th century. More compositions were added to the catalogue in the 21st century. The Anhang (Anh.; Annex) of the BWV lists over 200 lost, doubtful and spurious compositions.

https://en.wikipedia.org/wiki/Bach-Werke-Verzeichnis