1.
diverse, wide-ranging, manifold, many-branched
Describes something that branches out into many different areas or directions. Almost always used in the fixed expression 多岐にわたる (to span many areas). Literally means 'many branches' (of a path).
多岐 literally means "many branches" (of a road or path). It is almost exclusively used in the fixed expression 多岐にわたる.
Common expressions
多岐にわたる: to span many areas, to be wide-ranging
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Formal and written. Common in news articles, reports, academic writing, and business documents. In casual conversation, 幅広い or いろいろな would be preferred.