Tooth
السِّن
I keep noticing this little vertical peak.
I see a small pointed peak that rises off the baseline and drops back down — that's a tooth (سن). Once I started counting them, I realized they're what gives Arabic its visible rhythm: a row of teeth is a beat the eye can follow across a word.
Visual Impact
Teeth show up as repeated peaks (like a wave of small spikes), and also as tooth-like stroke units that structure many connected letters in text styles. Their height, sharpness, and spacing strongly affect clarity, especially at small sizes, because crowded or blunt teeth can make letters merge and reduce legibility.