Answer
adjective
1.
first in order of importance; main.
"the country's principal cities"
Similar:
main
chief
primary
leading
foremost
first
most important
predominant
dominant
(most) prominent
key
crucial
vital
essential
basic
staple
critical
pivotal
salient
prime
central
focal
premier
paramount
major
ruling
master
supreme
overriding
cardinal
capital
preeminent
ultimate
uppermost
highest
utmost
top
topmost
arch-
number-one
Opposite:
minor
subordinate
subsidiary
2.
(of money) denoting an original sum invested or lent.
"the principal amount of your investment"
noun
1.
the person with the highest authority or most important position in an organization, institution, or group.
"a design consultancy whose principal is based in San Francisco"
Similar:
boss
chief
chief executive (officer)
CEO
chairman
chairwoman
managing director
MD
president
director
manager
employer
head
leader
ruler
controller
head honcho
gaffer
governor
guv'nor
2.
a sum of money lent or invested, on which interest is paid.
"the winners are paid from the interest without even touching the principal"
Similar:
capital sum
capital
capital funds
working capital