principally

As an adverb principally

is in a primary manner; pertaining to the principal of a matter.

As an adjective undefined is

lacking a definition or value.

As adverbs the difference between principally and mostly

is that principally is in a primary manner; pertaining to the principal of a matter while mostly is mainly or chiefly; for the most part; usually, generally, on the whole.

As adverbs the difference between principally and extensively

is that principally is in a primary manner; pertaining to the principal of a matter while extensively is in an extensive manner, widely.

As adverbs the difference between specially and principally

is that specially is for a special purpose while principally is in a primary manner; pertaining to the principal of a matter.

As adverbs the difference between principally and fundamentally

is that principally is in a primary manner; pertaining to the principal of a matter while fundamentally is to the very core of the matter.

As adverbs the difference between largely and principally

is that largely is in a widespread or large manner while principally is in a primary manner; pertaining to the principal of a matter.

Expressly is a related term of principally.

As adverbs the difference between expressly and principally

is that expressly is in an expressive or explicit manner while principally is in a primary manner; pertaining to the principal of a matter.

Markedly is a related term of principally.

As adverbs the difference between markedly and principally

is that markedly is while principally is in a primary manner; pertaining to the principal of a matter.

As adverbs the difference between exclusively and principally

is that exclusively is to the exclusion of anything or anyone else; solely or entirely while principally is in a primary manner; pertaining to the principal of a matter.