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docs/en/reference/EXPRESSION.md

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+# EXPRESSION
+
+A named two-operand arithmetic expression. Reading the variable's value recomputes `OPERAND1 OPERATOR OPERAND2` in the current context every time, so the result tracks live changes to the input variables.
+
+Operands may be numeric literals, variable names, or bracketed sub-expressions (see [Arithmetic](../engine/arithmetic.md)). `EXPRESSION` exposes no script methods.
+
+## Fields
+
+### OPERAND1
+
+```
+STRING OPERAND1
+```
+
+Left-hand operand of the expression.
+
+### OPERAND2
+
+```
+STRING OPERAND2
+```
+
+Right-hand operand of the expression.
+
+### OPERATOR
+
+```
+STRING OPERATOR
+```
+
+Binary operator applied to the operands. Accepted values:
+
+| Value | Operation |
+| --- | --- |
+| `ADD` | addition |
+| `SUB` | subtraction |
+| `MUL` | multiplication |
+| `DIV` | division |
+| `MOD` | modulo |
+
+The result-type rules (integer vs floating-point) mirror those of ordinary script arithmetic — see [Arithmetic — typing rule](../engine/arithmetic.md#typing-rule).
+
+## Signals
+
+### ONINIT
+
+Fired when the object is initialised.
+
+### ONSIGNAL
+
+Fired when a signal arrives (see [Events and signals](../engine/events.md#onsignal)).