Unit 1, Lesson 1
discomfort
disconnect
dishonest
disobey
disqualify
nondairy
nonliving
nonremovable
nonspecific
nonstick
reappear
rearrange
rediscover
refreeze
retrace
uncooked
uneventful
unidentified
unimpressed
untangle
Challenge Words
disarray
nonverbal
unconscious
Unit 1, Lesson 2
applauded
bargaining
boasted
burying
concentrated
concluded
doubling
grumbled
guessing
identifying
informed
lectured
marveled
omitted
proposing
replied
stammering
suspending
vanishing
whirling
Challenge Words
analyzing
evacuated
immigrating
Unit 1, Lesson 3
aisle
content
desert
dew
due
excuse
I’ll
isle
lead
muscle
mussel
object
palm
pitcher
root
rung
side
sighed
story
wrung
Challenge Words
proceeds
stationary
stationery
Unit 1, Lesson 4
breezy
dusty
entirely
exactly
firmly
forcefully
graceful
grainy
gratefully
healthful
moody
peaceful
powerless
spotless
stormy
successful
swiftly
thoughtless
weightless
worthless
Challenge Words
flawless
historically
purposeful
Unit 1, Lesson 5
activity
admiration
admission
collision
concussion
decoration
digestion
division
exception
generosity
personality
humidity
identity
occasion
pollution
population
profession
punctuation
satisfaction
session
Challenge Words
agility
compassion
excursion
Unit 2, Lesson 1
angriest
best
better
biggest
bossiest
brighter
clumsiest
crunchier
deadliest
fiercest
fresher
lovelier
messier
sadder
scariest
steepest
thirstier
windier
worse
worst
Challenge Words
noisiest
slimier
stingiest
Unit 2, Lesson 2
autobiography
autofocus
autograph
automatic
automotive
autopilot
bibliography
cartography
megaphone
microphone
paragraph
phonics
phonograph
saxophone
telegram
telemarketer
telescope
television
televise
xylophone
Unit 2, Lesson 3
attractive
consign
contract
designer
detract
dictator
diction
dictionary
extract
indicate
manager
mandate
manipulate
manual
manufacture
prediction
protractor
resign
signature
significant
Challenge Words
abstract
predicament
maneuver
Unit 2, Lesson 4
addresses
avocados
beliefs
calves
computers
earthquakes
eyelashes
fireflies
journeys
kidneys
monkeys
pianos
potatoes
scarves
strawberries
supplies
thieves
toolboxes
volcanoes
watches
Challenge Words
sopranos
responsibilities
echoes
Unit 2, Lesson 5
bison
cacti
children
deer
elk
feet
fish
fungi
geese
lice
mice
moose
offspring
oxen
people
salmon
series
sheep
species
women
Challenge Words
alumni
axes
bacteria
Unit 3 Lesson 1
cell phone
check-in
father-in-law
good-looking
high school
jumping jack
life jacket
merry-go-round
old-fashioned
one-third
paper clip
ready-made
right angle
rocking horse
salad dressing
self-service
sleeping bag
time line
toll-free
well-dressed
Challenge Words
physical education
respiratory system
well-dressed
Unit 3-Lesson 2
additional
agreement
amusement
annual
argument
assignment
department
educational
enrollment
environment
excitement
improvement
musical
original
personal
political
renewal
settlement
treatment
tropical
Challenge Words
continental
entertainment
mechanical
Unit 3, Lesson 3
agreeable
available
believable
convertible
dependable
deport
divisible
enjoyable
export
import
important
impossible
incredible
porter
preventable
responsible
reversible
sensible
transportation
washable
Challenge Words
legible
portfolio
unforgettable
Unit 3, Lesson 4
automobile
bookmobile
commotion
demote
emotional
mobile
mobility
mobilize
motel
motility
motion
motivate
motive
motorist
moveable
movement
promote
remote
removal
snowmobile
Challenge Words
immobile
motivational
promotional
Unit 3, Lesson 5
intercept
intercom
interim
interrupt
intertwine
overjoyed
overload
overrated
overreact
overweight
subheading
submarine
submerge
subway
subzero
undercooked
underfed
underfoot
underpass
understudy
Challenge Words
intermission
subconscious
undervalue
Unit 4, Lesson 1
analogy
catalog
centimeter
cyclops
diameter
encyclopedia
epilogue
geocentric
geode
geography
geologist
geometry
logical
logo
millimeter
motorcycle
perimeter
speedometer
tricycle
unicycle
Challenge Words
apogee
barometer
cyclist
Unit 4, Lesson 2
activist
carnivorous
cartoonist
cautious
chemist
colonist
cyclist
ferocious
florist
furious
gracious
guitarist
journalist
marvelous
mysterious
numerous
optimist
ridiculous
venomous
zoologist
Challenge Words
anonymous
courageous
psychologist
Unit 4, Lesson 3
coauthor
coeducation
coexist
cooperate
coordinate
coproduce
forecast
forego
forerunner
foresee
foresight
forewarn
foreword
misbehave
misfortune
mishap
misinform
misrepresent
misunderstand
misuse
Challenge Words
coincidence
foreboding
misconduct
Unit 4, Lesson 4
deactivate
deconstruct
deflate
dehydrate
derail
illegal
illegible
illiterate
illogical
imbalance
immature
immovable
impractical
improper
inaccurate
inappropriate
inefficient
infinite
infrequent
injustice
Challenge Words
decontaminate
impartial
incompetent
Unit 4, Lesson 5
antibiotic
audible
audience
audio
audiobook
audiology
audiotape
audiovisual
auditorium
auditory
biodegradable
biodiversity
biographer
biography
biologist
biology
biomes
biopsy
biosphere
inaudible
Challenge Words
microbiologist
audiologist
symbiotic
Unit 5, Lesson 1
conscript
innate
inscribe
inscription
international
manuscript
national
nationalism
nationality
native
naturalist
naturalized
neonatal
nondescript
postscript
prescribe
scribble
scribe
script
transcript
Challenge Words
circumscribe
naturalistic
naturalization
Unit 5, Lesson 2
aquatic
artistic
athletic
awaken
engrave
enlighten
enlist
enrage
envision
exhale
expire
exterminate
extinguish
exude
forbidden
majestic
moisten
strengthen
sweeten
volcanic
Challenge Words
aeronautic
enamored
explosion
Unit 5, Lesson 3
antibodies
antifreeze
antiseptic
antisocial
antivirus
geothermal
photocopy
photogenic
photograph
photosynthesis
progeny
promotion
propeller
proponent
proposal
telephoto
thermal
thermometer
thermos
thermostat
Challenge Words
antibacterial
hypothermia
propagate
Unit 5, Lesson 4
abbreviate
accelerate
adventure
brotherhood
captivate
capture
complicate
dedicate
falsehood
feature
fracture
girlhood
irritate
knighthood
likelihood
nature
originate
picture
sisterhood
statehood
Challenge Words
daughterhood
procrastinate
straightforward
Unit 5, Lesson 5
bipeds
deflect
dislocate
expedite
impede
local
locate
location
locomotive
millipede
peddler
pedestal
pedestrian
pedigree
pedometer
reflect
reflection
reflective
reflector
relocate
Challenge Words
allocate
echolocation
expedition
Unit 6, Lesson 1
activity
applauded
bargaining
breezy
collision
concentrated
desert
dishonest
excuse
gratefully
identifying
identity
muscle
nondairy
population
rearrange
sighed
successful
uneventful
worthless
Challenge Words
evacuated
excursion
unconscious
Unit 6, Lesson 2
angriest
automatic
bibliography
cacti
crunchier
extract
fungi
kidneys
lovelier
manufacture
megaphone
people
potatoes
prediction
scarves
significant
species
strawberries
television
worst
Challenge Words
calligraphy
maneuver
responsibilities
Unit 6, Lesson 3
additional
agreeable
assignment
believable
commotion
educational
emotional
excitement
high school
interrupt
merry-go-round
moveable
overreact
paper clip
promotion
responsible
submerge
transportation
undercooked
well-dressed
Challenge Words
entertainment
immobile
intermission
Unit 6, Lesson 4
auditorium
biodegradable
biography
cautious
chemist
cooperate
coordinate
dehydrate
encyclopedia
foreword
geography
illegible
impractical
inaudible
inefficient
logical
millimeter
misfortune
venomous
zoologist
Challenge Words
anonymous
coincidence
impartial
Unit 6, Lesson 5
abbreviate
antiseptic
athletic
dedicate
envision
extinguish
innate
likelihood
manuscript
national
originate
peddler
pedestrian
photograph
prescribe
proposal
reflection
relocate
strengthen
thermometer
Challenge Words
expedition
hypothermia
treasure