alternate
alternative
auxiliary
collateral
incident
incidental
indirect
junior
low-level
minor
second-string
secondary coil
secondary remiges
secondary strata
secondhand
stand-by
subordinate
subsidiary
substitute
supplemental
supplementary
thirdhand
tributary
utility
vicarious
Janus-like
Maxwell triangle
Munsell scale
accessory
accident
accidental
addendum
addition
additional
adjunct
adscititious
adventitious
advocate
agent
alter ego
ambidextrous
amicus curiae
analogy
ancillary
appendage
appurtenance
appurtenant
ascititious
assistant
attorney
backup
backup man
bifacial
bifold
biform
bilateral
binary
binate
biparous
bivalent
borrowed
casual
champion
change
changeling
chromatic circle
chromatic spectrum
chromaticity diagram
circumstantial
cog
color circle
primary
coil
formation
principal
specific
vital