The triolet

https://www.poets.org/poetsorg/text/triolet-poetic-form

“Though some employed the triolet as a vehicle for light or humorous themes,Thomas Hardy recognized the possibilities for melancholy and seriousness, if the repetition could be skillfully employed to mark a shift in the meaning of repeated lines.

In “How Great My Grief,” Hardy displays both his mastery of the triolet and the potency of the form:

     How great my grief, my joys how few,
Since first it was my fate to know thee!
—Have the slow years not brought to view
How great my grief, my joys how few,
Not memory shaped old times anew,
Nor loving-kindness helped to show thee
How great my grief, my joys how few,
Since first it was my fate to know thee?

The first line, “How great my grief, my joys how few,” is, in its two subsequent appearances, modified by the movement of time in the poem. Initially, the line assumes a declarative position, indicating the subject and tone of the poem, one of grief and love lost. By its third iteration, after several queries to the person being addressed, the line takes on the added weight of the speaker’s astonished grief that the addressee has not, despite the years, recognized the speaker’s profound sense of loss.”