What Is a Stem in Typography?

If you want to see the skeleton of a letter, look for the stems. The straight line in l is a stem. So are the vertical strokes in h, d, p, T, E, F and I. In an italic or script face the stems lean, but they still do the same job: they carry the main weight of the letter and give the eye something regular to follow along a line of text.

Stem weight and rhythm

When a type designer sketches a new alphabet, the first decision is stem thickness. A light weight has thin stems and a bold weight has stems several times thicker, and the other strokes are built to match. If you set several letters in a row, the pattern of verticals creates a rhythm like fence posts: hill, mill and illumination are strongly rhythmic because they have many stems.

Spacing follows from that rhythm. In a font the space between two stems, such as in ll or nn, becomes the reference for all other pairs. Rounder shapes get less space than straights, diagonals get less than rounds. When you hand-letter, set a pair of stems the right distance apart and judge everything else against it. The idea is the same as the one behind kerning: the white space between stems sets the beat.

Stems and contrast

In typefaces with high contrast, stems are thick and the horizontal strokes thin. In a Didone-style serif such as Bodoni, the stems are many times thicker than the hairlines. In a monoline sans-serif, stems and horizontals are nearly equal. Contrast relates to the writing tool. A broad-edge pen held at a fixed angle produces thick vertical stems and thin horizontals, which is why old-style serif faces have this look. A pointed pen or brush pen makes thick downstrokes and thin upstrokes, which is why script fonts have heavier stems that slope.

Real stems are often not perfectly uniform. Many typefaces thicken stems slightly in the middle or taper them toward the top to counter an optical effect: a perfectly uniform line can look pinched where it meets curves. Horizontal strokes are made a little thinner than stems for the same reason, because horizontals look heavier to the eye.

Stems in lettering and calligraphy

For handwriting and calligraphy, the stem is where you practice first. Standard drills are rows of straight downstrokes, then slanted downstrokes at a steady angle, then stem plus entry and exit strokes. Our calligraphy for beginners guide uses these as the foundation drills, since every letter built on a stem inherits any slant or weight problem. Stems can be extended upward as ascenders or downward as descenders, and where the stem stops on the baseline is where a serif or exit stroke begins.

If you are copying a lettering style, use a slant guide: a set of parallel lines at a fixed angle to the baseline, for example about 55 degrees for traditional copperplate-style scripts, or a steeper angle for modern calligraphy. Every stem should follow the guides.

Stems in fancy text

Because Unicode styles are fixed shapes, you cannot set stem width, but you can choose it. The bold styles in our generators use fonts with thicker stems, and monospace styles use uniform stems with slab feet. The text decorator adds borders around stems and letters rather than changing them.

Common confusions

• Stem is not the same as ascender. An ascender is the part of a stem that rises above the x-height; the stem is the whole stroke.
• Not every straight stroke is a stem. A horizontal bar in e or T is a bar or crossbar, and the vertical in a capital E is the stem.
• Italic stems are slanted. In oblique styles the stems are sloped, not curved.