What is the stroke used to create part of the upper portion in Celtic letters E, F, and G called?

The correct term for the stroke used in the upper portion of Celtic letters E, F, and G is "fillet." In calligraphy, a fillet typically refers to a slender decorative line or stroke that adds elegance and detail to the letterforms. In the context of Celtic letters, fillets are integral in creating the distinctively intricate and ornate nature that characterizes this style, enhancing the visual appeal and complexity of the glyphs.

Understanding this term within the world of calligraphy is crucial because it helps you grasp the various components that contribute to the overall aesthetic of letterforms. The use of fillets in Celtic letters showcases the unique balance between structure and decorative elements, highlighting how stylistic choices can impact the effectiveness of a design.