A SD (Secure Digital) is a memory card format for use in portable devices. It can retain stored information even when not powered.
SaaS
SAIC
SAW Filter
SD
SDIO
Sensitivity
Serial Interface
Serial Port
SGSN
SHA
Short Range RF
SIM
SIM Access Profile
Single Band
SiRF
Smart Grid
Smart Metering
SMD
SMS
SMT
SMTP
SOC
SRRC