CHIEFLY
chiefly, principally, primarily, mainly, in the main
(adverb) for the most part; “he is mainly interested in butterflies”
Source: WordNet® 3.1
Etymology
Adverb
chiefly (comparative more chiefly, superlative most chiefly)
(focus) Especially or primarily; above all.
(focus) Mainly or principally; almost entirely.
Synonyms
• (above all): first and foremost, particularly; see also above all
• (almost entirely): by and large, for the most part, largely; see also mostly
Adjective
chiefly (comparative chieflier, )
of or relating to a chief
Source: Wiktionary
Chief"ly, adv.
1. In the first place; principally; preëminently; above; especially.
Search through this garden; leave unsearched no nook; But chiefly
where those two fair creatures lodge. Milton.
2. For the most part; mostly.
Those parts of the kingdom where the . . . estates of the dissenters
chiefly lay. Swift.
Source: Webster’s Unabridged Dictionary 1913 Edition