Buying terms glossary

By TwelveTabs · Updated

These are the spec terms our buying guides use, in plain English. Each links to a guide where the term matters. General information, not medical advice.

4K
A screen about 3,840 by 2,160 pixels, four times the pixels of 1080p. Sharper text and detail, if the screen is big enough to show it. See Best Screens for Mac Mini.
ANC (active noise cancelling)
Microphones listen to outside sound and the headphones play the opposite wave to cancel it. It works best on steady low sounds such as engines and fans. See Best Noise-Cancelling Headphones.
BPA-free
Made without bisphenol A, a chemical once common in hard plastic bottles and food containers. See Best Running Water Bottles.
BTU
British thermal units per hour: how much cooling or heating power an air conditioner has. Bigger rooms need more. See Best Window Air Conditioners.
CADR
Clean air delivery rate. A tested number for how fast an air purifier cleans smoke, dust and pollen from the air. Higher is faster, so match it to your room size. See Best Air Purifiers for Pets.
Ceramides
Fats found naturally in the skin's outer layer. In skincare they are used to support the skin barrier and cut dryness. See Best Milk Toners.
CFM
Cubic feet per minute: how much air a blower or fan moves. Air speed is a separate number, so look at both. See Best Leaf Blowers.
Denier
A measure of thread thickness. Low denier is sheer and light, high denier is opaque and thick. See Best Tights for Women.
DPI
Dots per inch. How sensitive a mouse is: a higher number moves the cursor farther for the same movement of your hand. See Best Office Mice.
DWR
Durable water repellent. A coating that makes water bead up and roll off a jacket's fabric. It wears off with use and is not the same as a waterproof membrane. See Best Waterproof Jackets for Women.
fps
Frames per second: how many pictures a camera records or a screen shows each second. 24 looks like film, and 60 is smoother for fast action. See Best Cameras and Camcorders.
GSM
Grams per square meter: how heavy a fabric is. Heavier towels are thicker and more absorbent but dry more slowly. See Best Bath Towels.
HEPA
A filter standard. A true HEPA filter catches at least 99.97 percent of particles 0.3 microns wide. See Best Air Purifier Humidifier Combos.
Hyaluronic acid
An ingredient that binds water, so it holds moisture on the skin's surface. See Best Drugstore Eye Cream.
Hybrid mattress
A mattress with a coil spring core and foam or latex layers on top. More bounce and airflow than an all-foam bed. See Best Mattresses.
IPS
A type of LCD panel known for wide viewing angles and steady color when you look from the side. See Best Screens for Mac Mini.
IPX rating
A water-resistance grade. IPX4 survives splashes. IPX7 survives being under water for a short time: up to 1 meter for 30 minutes. The X means it was not rated for dust. See Best Swimming Headphones.
Latency
The delay between an action and the sound or picture. For wireless earbuds, low latency keeps the sound in sync when you game. See Best Gaming Earbuds.
Lumbar support
Support for the curve of your lower back. In a chair, a lumbar curve or adjustable pad keeps your spine from slumping. See Best Ergonomic Desk Chairs.
Lumens
How much light a bulb or flashlight puts out. More lumens is brighter, and also drains the battery faster. See Best Flashlights.
mAh
Milliamp-hours: how much charge a battery holds. A bigger number runs longer, or charges more devices, before it needs a recharge. See Best Rechargeable Batteries.
Memory foam
Foam that softens with body heat and slowly springs back. It hugs the body, and it can sleep warm. See Best Dorm Mattress Toppers.
Merino
Wool from merino sheep. It is fine and soft, resists odor and keeps you warm even when damp. See Best Summer Hiking Socks.
Mirrorless
A camera with interchangeable lenses and no mirror box. It is smaller than a DSLR and shows a live electronic view. See Best Mirrorless Cameras.
Moisture-wicking
A fabric that pulls sweat off your skin to the outer surface, so it dries fast. See Best Golf Shirts.
Niacinamide
A form of vitamin B3 used in skincare to even out tone and support the skin barrier. See Best Eye Serums.
Non-comedogenic
Made to avoid clogging pores. There is no legal standard for the label in the US, so it is a claim, not a guarantee. See Best Drugstore Face Wash.
NSF
A group that tests and certifies water filters and other products. Look for the standard: NSF/ANSI 53 covers health contaminants such as lead. See Best Home Water Filters.
NVMe
A fast way to connect a solid-state drive straight to a computer's PCIe lanes. It is much quicker than the older SATA connection. See Best M.2 SSDs for Gaming.
OLED
A screen where every pixel makes its own light, so black is truly black. Contrast is usually better than a regular LCD. See Best Ultrawide Monitors.
Paraben-free
Made without parabens, a family of preservatives. Many brands drop them because buyers ask, and the product still needs another preservative. See Best Aluminum-Free Deodorants.
Qi2
The wireless charging standard with a magnet ring, like MagSafe, so the phone and charger line up. It charges at up to 15W. See Best Wireless Chargers for iPhone.
Refresh rate
How many times per second a screen redraws the picture, in hertz (Hz). 120Hz looks smoother than 60Hz for fast motion such as sports and games. See Best TVs for Sports.
Retinol
A form of vitamin A used on skin for fine lines and uneven tone. Start with a low strength a few nights a week: it makes skin more sensitive to sun. See Best Over the Counter Retinol.
RPM
Revolutions per minute: how fast a blade or motor spins. A higher number cuts faster, but blade and power matter too. See Best Circular Saws.
SPF
Sun protection factor: how well a sunscreen blocks UVB, the rays that burn. Higher numbers block a little more. Broad spectrum means it also covers UVA. See Best Sunscreens.
SSD
Solid-state drive. Storage with no moving parts, so it is faster, quieter and tougher than a hard disk. See Best External SSDs.
Sulfate-free
Made without harsh cleansing agents such as sodium lauryl sulfate. Gentler on dry or curly hair, but it lathers less. See Best Clarifying Shampoo for Curly Hair.
Thread count
Threads per square inch of fabric. A very high number is not always better: the length of the cotton fiber matters more. See Best Cotton Sheets.
UPF
Ultraviolet protection factor for fabric. UPF 50 lets through about 2 percent of UV rays. See Best Neck Gaiters.
Wi-Fi 6
The 802.11ax Wi-Fi standard. It handles many devices at once better than Wi-Fi 5, but both the router and the device need it. See Best Mesh Wi-Fi Systems.

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