SD
SD may refer to any of the following:
1. Short for standard definition, SD is a resolution of video media measuring 720 x 480 pixels and has an aspect ratio of 4:3. Today, SD is the lowest quality, coming in behind the HD, FHD (Full High Definition), QHD (Quad High Definition), and 4K and 8K resolutions (UHD). Consequently, SD is mostly phased out of modern devices.
2. Short for Secure Digital, an SD card is a memory card. See our SD card definition for more information and related terms.
3. When describing a video format, SD is short for super density and is a format that helped create the DVD (digital versatile disc) standard in 1993.
4. Short for single-sided diskette or single-density diskette, SD is a diskette that supports writing on one side of the diskette. See our single-density diskette definition for more information and related terms.
5. The Internet domain suffix .sd is short for Sudan.
6. SD is an acronym sometimes used for sugar daddy.