Sans-Serif Fonts

Interfaces and data: humanist or neo-grotesque with large x-height , open forms, and unambiguous I/l/1 . This is the sans's home turf.
Long body text: possible and increasingly common — pick a humanist with true italics and comfortable spacing rather than a stark geometric, whose uniform rhythm tires the eye over paragraphs.
Branding and headlines: geometrics and characterful grotesques shine here; this is where personality is worth its legibility price.
Signage and wayfinding: humanist, always — it's why airports look the way they do.

Sans-serifs — letterforms without finishing strokes — are barely two centuries old, which makes them the disruptive newcomers of type history. Today they dominate screens, signage, and interfaces so completely that "clean and modern" is practically their legal definition. But "sans-serif" hides three families with genuinely different personalities.

The three temperaments

Grotesques (and their tidier "neo-grotesque" descendants: Helvetica, Univers, and modern heirs like Inter) aim for neutrality — uniform strokes, closed forms, horizontal terminals, no gesture. They are the institutional voice: airports, forms, corporations. The history of Helvetica is the history of this ambition. Geometrics (Futura and its century of descendants) build letters from circles and straight lines; they read as designed, aspirational, engineered — see the Futura story. Humanists (Gill Sans, Frutiger, and moderns like Source Sans) keep the skeleton of calligraphic writing under serifless skin: open apertures, varied widths, a warmth the other two branches deliberately lack — and, not coincidentally, the best small-size legibility of the three.