How does the French alexandrine use syllable count and caesura?

The French alexandrine is the leading measure in French poetry, defined by a specific structural arrangement of syllables and pauses.1

Syllable Count

The alexandrine consists of a line of 12 syllables. Its metrical principle is based on stress according to sense, which allows for flexibility in how the line is articulated while maintaining its fundamental length.1

Caesura

The line is structured around a major medial caesura, which is a pause that occurs after the 6th syllable. This division effectively splits the 12-syllable line into two equal halves. To maintain the rhythm, the line features:1
* A major stress on the 6th syllable, immediately preceding the medial pause.1
* A major stress on the final (12th) syllable.1
* One secondary accent within each of the two half-lines.1

Because six syllables correspond to a natural breath group, this structure is highly adaptable for various forms of expression, ranging from narrative description to complex emotions. In the late 19th century, this structure was sometimes modified into a three-part line known as a trimètre, though the traditional alexandrine remains a cornerstone of French verse.1