Full of content or substance; meaningful and substantial in value or significance.
From 'content' (meaning substance or material) plus -ful (a suffix meaning 'full of'). The word emphasizes abundance of meaningful material rather than mere quantity.
A 'contentful' book versus a 'lengthy' book—you could have 300 pages that are boring or 200 pages absolutely packed with ideas and meaning; that's the difference this word captures.
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