Guides to tools, home products and outdoor gear use a lot of shorthand. This Top Discounts glossary explains 25 terms that show up on product pages and in reviews, so you can read a spec sheet with more confidence.
The definitions are general and written to be neutral. A manufacturer may use a term a little differently, so check the product page when a number matters to your decision. Terms are listed alphabetically.
- Amp-hour (Ah)
- A measure of how much charge a battery holds. A higher number usually means longer runtime on the same tool. Ah does not tell you how powerful the tool is.
- Brushless motor
- An electric motor that uses electronics instead of carbon brushes to switch current. It generally runs more efficiently and has fewer parts that wear down. Brushless tools often cost more than brushed ones.
- CFM
- Cubic feet per minute, a measure of airflow. Air compressors and vacuums list it. For a compressor, CFM is usually given at a stated pressure, so compare it at the same PSI.
- Chuck
- The part of a drill that grips the bit. Keyless chucks tighten by hand, while keyed chucks need a small tool. Common sizes include 3/8 inch and 1/2 inch.
- Denier
- A unit that describes the thickness of a fiber. A higher number generally means a thicker, heavier yarn. It is one clue about how tough a fabric is, along with weave and coating.
- DWR
- Short for durable water repellent, a finish on fabric that makes water bead up and roll off. It is not the same as waterproofing. The finish wears off over time and can be reapplied.
- Fill power
- A measure of how much space an ounce of down fills. Higher numbers mean the down is lighter for the warmth it provides. It is used for jackets and sleeping bags.
- GFCI
- A ground-fault circuit interrupter. It cuts power quickly when it detects current leaking along an unintended path. GFCI outlets are common in kitchens, bathrooms and outdoor areas.
- Grit
- A number that describes the size of the abrasive particles on sandpaper. A lower number means coarser paper that removes material faster. A higher number gives a smoother finish.
- Horsepower
- A unit of power, often listed on saws, compressors and pumps. Peak ratings and continuous ratings can differ a lot. Look for which one the maker means.
- Hydrostatic head
- A waterproof rating given in millimeters. It shows how tall a column of water a fabric can hold before it leaks. Tents and rain jackets often list it.
- Impact driver
- A tool that adds quick rotational taps while it turns. This helps drive long screws and bolts without as much strain on the user. It is different from a hammer drill.
- Kerf
- The width of the cut a saw blade makes. A thinner kerf removes less material and needs less effort. It matters when you want to plan cuts in a board.
- Lithium-ion battery
- A rechargeable battery type used in most modern cordless tools. It is lighter than older nickel-based packs and holds its charge when stored. It should be kept within the temperature range the maker lists.
- Lumen
- The unit for the total visible light from a source. Headlamps, work lights and lanterns list it. More lumens means more light, but it does not show how far the beam reaches.
- PSI
- Pounds per square inch, a measure of pressure. It is used for air compressors, pressure washers and tires. A higher PSI means more force, not necessarily more air volume.
- R-value
- A measure of resistance to heat flow. Insulation, sleeping pads and similar products list it. A higher number means better insulation.
- Ripstop
- A woven fabric with thicker threads added in a grid pattern. The extra threads help keep a small tear from spreading. It is common in tents, jackets and packs.
- RPM
- Revolutions per minute, which shows how fast a motor or blade turns. Drills and saws often list a range. A higher RPM is not always better, because the right speed depends on the material.
- Season rating
- A label such as three-season that describes the weather a tent or sleeping bag is designed for. There is no single official standard behind every label. Treat it as a rough guide and compare the actual specs.
- Torque
- A twisting force, often listed in inch-pounds or foot-pounds. In drills and impact drivers it shows how hard the tool can turn a fastener. More torque helps with large screws and hard materials.
- Variable speed
- A feature that lets the user change how fast a tool runs, often with a trigger. It gives better control when starting a screw or cutting delicate material. Some tools also have a speed dial.
- Voltage
- The electrical potential that drives current. On cordless tools, it often hints at power class, such as 12 volt or 20 volt. Compare tools within the same brand line, since labeling differs.
- Watt
- A unit of power. Corded tools, heaters and lights list it. A higher wattage means the item uses more power, which is not always the same as doing more work.
- Wire gauge
- A number that describes how thick a wire is, usually on the American Wire Gauge scale. A smaller number means a thicker wire that can carry more current. It matters when you choose an extension cord.