Display screen or portion thereof with a transitional graphical user interface

[0001]FIG. 1 is a front view of a display screen or portion thereof with a transitional graphical user interface;

[0002]FIG. 2 is a second image thereof;

[0003]FIG. 3 is a front view of the display screen or portion thereof with a transitional graphical user interface showing a second embodiment thereof;

[0004]FIG. 4 is a second image thereof;

[0005]FIG. 5 is a front view of a display screen or portion thereof with a transitional graphical user interface showing a third embodiment thereof;

[0006]FIG. 6 is a second image thereof;

[0007]FIG. 7 is a front view of the display screen or portion thereof with a transitional graphical user interface showing a fourth embodiment thereof; and,

[0008]FIG. 8 is a second image thereof.

[0009]The longer length broken lines showing a display screen and a display screen boundary are included for illustrating environmental structure and do not form part of the claimed design. The other broken lines represent elements that form no part of the claimed design.

[0010]In the first embodiment, the appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-2. In the second embodiment, the appearance of the transitional image sequentially transitions between the images shown in FIGS. 3-4. In the third embodiment, the appearance of the transitional image sequentially transitions between the images shown in FIGS. 5-6. In the fourth embodiment, the appearance of the transitional image sequentially transitions between the images shown in FIGS. 7-8. For each of the first, second, third and fourth embodiments, the process or period in which one image transitions to another forms no part of the claimed design.