Anything related to depletion-mode devices (e.g. depletion MOSFETs, JFETs), i.e those semiconductor devices (largely FETs) whose output current (e.g. \$I_D\$) may be non-zero when the controlling signal (e.g. \$V_{GS}\$) is zero.
Anything related to depletion-mode devices (e.g. depletion MOSFETs, JFETs), i.e those semiconductor devices (largely FETs) whose output current (e.g. \$I_D\$) may be non-zero when the controlling signal (e.g. \$V_{GS}\$) is zero.