CDL words, explained in plain English
304 words from the CDL knowledge tests. Each one has a short meaning, the way the test asks about it, and the questions that use it.
Searches English terms, other names and your language.
Start here: the 25 words that decide the test
The words that appear in the most CDL test questions. Learn these first.
- commercial driver's license
- hazardous materials
- commercial motor vehicle
- warning devices
- placard
- headlights
- turn signals
- triples
- DUI
- fatigue
- brake pedal
- air brakes
- hazmat endorsement
- parking brake
- pre-trip inspection
- high beams
- stopping distance
- tank vehicle
- disqualification
- traction
- anti-lock braking system
- following distance
- shipping paper
- speed limit
- hazard class
Browse by topic
- Air brakes42 terms · in 385 questions
- Combination vehicles, doubles and triples27 terms · in 333 questions
- Hazardous materials12 terms · in 281 questions
- Tank vehicles8 terms · in 116 questions
- Passenger and school bus8 terms · in 79 questions
- Pre-trip inspection parts70 terms · in 891 questions
- Driving and safety50 terms · in 936 questions
- Licence, rules and roadside48 terms · in 757 questions
- Numbers and units on the test13 terms · in 739 questions
- Work and freight words26 terms · in 83 questions
All words A to Z
Every word in the glossary, grouped by topic.
Air brakes (42)
- air brakes
- air compressor
- air leakage rate
- air pressure gauge
- air tank
- alcohol evaporator
- anti-lock braking system
- application pressure gauge
- brake chamber
- brake drum
Show all 42 terms
- brake fade
- brake lag
- brake lining
- brake pedal
- controlled braking
- cut-in pressure
- cut-out pressure
- disc brakes
- drain valve
- dual air brake system
- emergency brake
- emergency braking
- emergency line
- engine brake
- glad hands
- governor
- hydraulic brakes
- low air pressure warning
- parking brake
- pushrod
- retarder
- S-cam
- safety valve
- service brake
- service line
- slack adjuster
- spring brakes
- stab braking
- tractor protection valve
- trailer air supply control
- trailer hand valve
- wig wag
Hazardous materials (12)
- emergency response guidebook
- hazard class
- hazardous materials
- hazardous materials table
- hazardous waste manifest
- hazmat endorsement
- identification number
- packing group
- placard
- placarded vehicle
Show all 12 terms
Tank vehicles (8)
Pre-trip inspection parts (70)
- accelerator
- air bags
- alternator
- ammeter
- applied air leak test
- battery
- brake hoses and lines
- bumper
- cargo doors
- catwalk
Show all 70 terms
- clutch pedal
- compressor belt
- control arm
- convex mirror
- door ties
- DOT bumper
- drag link
- drive shaft
- dual tire spacing
- emergency equipment
- exhaust system
- fifth wheel gap
- fifth wheel platform
- fire extinguisher
- fluid leaks
- frame
- fuel tank
- headlights
- heater and defroster
- hood
- horn
- hoses and wiring
- hub oil seal
- leaf spring
- license plate
- lighting indicators
- lights and reflectors
- lug nuts
- marker lights
- mirrors
- oil level
- oil pressure gauge
- pitman arm
- power steering reservoir
- radiator
- rim
- seat belt
- shifter
- shock absorber
- skid plate
- spare fuses
- splash guards
- spring brake pop-out test
- spring mounts
- static air leak test
- steering gear box
- steering linkage
- steering wheel play
- steps
- tie rod
- tires
- torsion bar
- tread depth
- turn signals
- valve stem
- warning devices
- water pump
- water temperature gauge
- windshield
- windshield wipers
Driving and safety (50)
- aggregate working load limit
- aggressive driving
- black ice
- blind spot
- blocking and bracing
- blood alcohol concentration
- brake failure
- braking distance
- cargo securement
- countersteering
Show all 50 terms
- cruise control
- curve speed
- distracted driving
- divided highway
- downgrade
- drive-wheel skid
- DUI
- escape ramp
- fatigue
- following distance
- front-wheel skid
- hazard lights
- high beams
- hydroplaning
- implied consent
- intersection
- lane change
- low beams
- merging
- passing
- perception distance
- reaction distance
- right-of-way
- safe speed
- shoulder
- skid
- speed limit
- stopping distance
- tailgating
- tarp
- tie-downs
- tire blowout
- total stopping distance
- traction
- two-lane road
- upgrade
- visibility
- wheel chocks
- work zone
- working load limit
Licence, rules and roadside (48)
- 11-hour limit
- 14-hour limit
- 30-minute break
- 34-hour restart
- 60/70-hour limit
- air brake restriction
- axle weight
- basic vehicle control skills test
- bridge formula
- Class A
Show all 48 terms
- Class B
- Class C
- commercial driver's license
- commercial learner's permit
- commercial motor vehicle
- disqualification
- DOT
- DOT physical
- doubles/triples endorsement
- driver vehicle inspection report
- Drug and Alcohol Clearinghouse
- electronic logging device
- endorsement
- English language proficiency
- entry-level driver training
- felony
- FMCSA
- gross combination weight
- gross combination weight rating
- gross vehicle weight
- gross vehicle weight rating
- hours of service
- knowledge test
- logbook
- medical examiner's certificate
- on-duty time
- out of service
- pre-trip inspection
- restriction
- roadside inspection
- skills test
- sleeper berth
- suspension
- tank and hazmat endorsement
- traffic violation
- training provider registry
- vision test
- weigh station
Numbers and units on the test (13)
- 0.04 BAC
- 10,001 pounds
- 26,001 pounds
- feet
- gallons
- inches
- low air warning pressure
- miles
- miles per hour
- pounds
Show all 13 terms
How to use this glossary
Read the short meaning first. Then read "On the test" — that line tells you what the questions ask.
Learn the English word. In most states the test is in English. The word in your language is a hint, not a replacement.
Open "See questions" to practice the real questions that use the word.
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