Extensively means over a wide area or in great depth. Travelled extensively, extensively researched, damaged extensively.
It is about coverage rather than intensity, which is the difference from intensively: farming extensively means using a lot of land lightly. In writing it is a favourite of biographies, where somebody has always travelled extensively.
1adverbextensivelyOver a wide area or in great depth.
“The book has been extensively revised for the new edition.”
extensively is a manner.
Latin
extensīvus
Middle English
extensive
English
extensive
English, today
extensively
From extensive + -ly. extensive comes from Middle English extensive, from Latin extensīvus. From late Middle English -, borrowed from Latin extensīvus, from Latin extensus.
Etymology from Wiktionary, CC BY-SA