| PLC | Programmable Logic Controller — industrial computer for automation |
| Soft-PLC | PLC implemented in software on general-purpose hardware |
| Ladder Logic | Visual programming language that mimics electrical relay circuits |
| Rung | A horizontal line of logic in a ladder program |
| Contact | Input element (XIC/XIO) — evaluates conditions |
| Coil | Output element (OTE/OTL/OTU) — executes actions |
| Scan | One complete execution cycle (read inputs → execute logic → write outputs) |
| Scan Time | Duration of one scan cycle (configurable 10–1000ms) |
| Forcing | Manual override of I/O values for testing |
| Branch | Parallel paths in a rung that implement OR logic |
| Decorator | Behavior modifier applied to a contact (timer, debounce, etc.) |
| Engine Context | Independent PLC instance with its own program and memory |
| Signal Router | Inter-context communication system |
| GPIO | General Purpose Input/Output — physical hardware pins |
| libgpiod | Linux library for modern GPIO access via character devices |
| HMI | Human-Machine Interface — visual operator panel |
| WebSocket | Bidirectional communication protocol between editor and engine |
| Headless | Operation without a graphical interface (service/daemon mode) |
| systemd | Linux service management system |