(1) See
HD Radio,
HD audio and
half-duplex.
(2) (
High
Definition) HD often refers to a high-resolution digital TV (see
HDTV). The HD designation is also used with many TV/video formats (see
HD analog formats and
HD formats).
(3) (
Hard
Disk,
Hard
Drive) For example, a 500GB HD is a 500 gigabyte hard disk. FD means floppy disk; today a distant memory. See
hard disk,
magnetic disk and
floppy disk.
(4) (
Hierarchical
Deterministic) The common type of cryptocurrency wallet. See
crypto wallet.
(5) (
High
Definition) A screen resolution of at least 1280x720 pixels. HD+ is 1480x720. See
DTV,
FHD,
720p and
screen resolution.
(6) (
High
Density) HD and DD (double density) were used in floppy disk designations. For example, 3.5" 1.44MB HD and 720KB DD or 5.25" 1.2MB HD and 360K DD. See
floppy disk.
HD and HD+ Screen Resolutions
In the Galaxy S7 smartphone (top) and S8 (bottom), the screen resolution can be reduced to save battery.