bar chart

A bar chart is a specific kind of chart that compares categories using rectangular bars proportional to their values. A competent speaker calls a bar chart 'a chart'.

A stacked bar chart IS a specific kind of bar chart: it uses the same basic bar encoding but subdivides each bar into compositional segments. A competent speaker would call a stacked bar chart 'a bar chart.' The INSTANCE_OF direction is correct: specific (stacked bar chart) → general (bar chart). Direction pinned per Law 11d: 'stacked bar chart' as a compositional bar chart variant.

Direction test: specific→general. A grouped bar chart IS a specific kind of bar chart — bars arranged in clusters to compare multiple categories side by side. A competent speaker would call a grouped bar chart 'a bar chart'. Nearest kind: bar chart (bar chart→chart already ACCEPTED, so chart is not the nearest kind).

A lollipop chart IS a specific kind of bar chart. It displays the same categorical comparison data but replaces the traditional bar rectangle with a thin line ending in a filled circle (the 'lollipop'). The encoding is identical — position and length encode value. A competent speaker would call a lollipop chart 'a bar chart' — it is a stylistic variant of the bar chart.

TESTED INSTANCE_OF: a gantt chart IS a specific kind of bar chart — it visualizes project schedules using horizontal bars representing tasks against a timeline. A competent speaker would call a Gantt chart 'a bar chart'. This is the nearest kind; 'chart' is too broad (Law 11e leap refused previously).

TESTED INSTANCE_OF: a waterfall chart IS a specific kind of bar chart. It displays sequential positive and negative values as bars extending from a running total, with green bars for increases and red bars for decreases. It shares the fundamental bar-based encoding of a bar chart but adds the running-total and sign-coding convention.

Bullet charts were created by Stephen Few as an evolution of the bar chart, adding performance targets, comparative measures, and qualitative ranges. The which-came-first test (Law 7) passes: bar charts predate and fed into the bullet chart design.

A grouped bar chart is a chart type that builds on the bar chart mechanism. It requires bars as its fundamental visual encoding element — grouped bar charts organize multiple bars per category using the bar-length encoding. Remove bar charts and grouped bar charts cease to function.