diff --git a/smnp/ast/node/expression.py b/smnp/ast/node/expression.py
index 4d0ea0d..f4b87f5 100644
--- a/smnp/ast/node/expression.py
+++ b/smnp/ast/node/expression.py
@@ -1,11 +1,22 @@
 from smnp.ast.node.operator import BinaryOperator
 from smnp.ast.node.term import TermParser
-from smnp.ast.node.valuable import Valuable
 from smnp.ast.parser import Parser
 from smnp.token.type import TokenType
 
 
-class Expression(Valuable):
+class Sum(BinaryOperator):
+    pass
+
+
+class Relation(BinaryOperator):
+    pass
+
+
+class And(BinaryOperator):
+    pass
+
+
+class Or(BinaryOperator):
     pass
 
 
@@ -16,28 +27,28 @@ def ExpressionParser(input):
         TermParser,
         [TokenType.PLUS, TokenType.MINUS],
         TermParser,
-        lambda left, op, right: Expression.withValue(BinaryOperator.withValues(left, op, right))
+        lambda left, op, right: Sum.withValues(left, op, right)
     )
 
     expr2 = Parser.leftAssociativeOperatorParser(
         expr1,
         [TokenType.RELATION, TokenType.OPEN_ANGLE, TokenType.CLOSE_ANGLE],
         expr1,
-        lambda left, op, right: Expression.withValue(BinaryOperator.withValues(left, op, right))
+        lambda left, op, right: Relation.withValues(left, op, right)
     )
 
     expr3 = Parser.leftAssociativeOperatorParser(
         expr2,
         [TokenType.AND],
         expr2,
-        lambda left, op, right: Expression.withValue(BinaryOperator.withValues(left, op, right))
+        lambda left, op, right: And.withValues(left, op, right)
     )
 
     expr4 = Parser.leftAssociativeOperatorParser(
         expr3,
         [TokenType.OR],
         expr3,
-        lambda left, op, right: Expression.withValue(BinaryOperator.withValues(left, op, right))
+        lambda left, op, right: Or.withValues(left, op, right)
     )
 
     ifElseExpression = Parser.allOf(
diff --git a/smnp/runtime/evaluators/expression.py b/smnp/runtime/evaluators/expression.py
index 88abfd0..4259444 100644
--- a/smnp/runtime/evaluators/expression.py
+++ b/smnp/runtime/evaluators/expression.py
@@ -1,3 +1,4 @@
+from smnp.ast.node.expression import Sum
 from smnp.ast.node.factor import NotOperator, Power, Loop
 from smnp.ast.node.identifier import FunctionCall, Assignment
 from smnp.ast.node.term import Product
@@ -19,6 +20,7 @@ def expressionEvaluator(doAssert=False):
         from smnp.runtime.evaluators.assignment import AssignmentEvaluator
         from smnp.runtime.evaluators.product import ProductEvaluator
 
+        from smnp.runtime.evaluators.sum import SumEvaluator
         result = Evaluator.oneOf(
             Evaluator.forNodes(FunctionCallEvaluator.evaluate, FunctionCall),
             Evaluator.forNodes(MinusEvaluator.evaluate, MinusOperator),
@@ -28,6 +30,7 @@ def expressionEvaluator(doAssert=False):
             Evaluator.forNodes(LoopEvaluator.evaluate, Loop),
             Evaluator.forNodes(AssignmentEvaluator.evaluate, Assignment),
             Evaluator.forNodes(ProductEvaluator.evaluate, Product),
+            Evaluator.forNodes(SumEvaluator.evaluate, Sum),
             AtomEvaluator.evaluate
         )(node, environment)
 
diff --git a/smnp/runtime/evaluators/sum.py b/smnp/runtime/evaluators/sum.py
new file mode 100644
index 0000000..bcb7f9f
--- /dev/null
+++ b/smnp/runtime/evaluators/sum.py
@@ -0,0 +1,40 @@
+from smnp.error.runtime import RuntimeException
+from smnp.runtime.evaluator import Evaluator
+from smnp.runtime.evaluators.expression import expressionEvaluator
+from smnp.type.model import Type
+
+
+class SumEvaluator(Evaluator):
+
+    @classmethod
+    def evaluator(cls, node, environment):
+        left = expressionEvaluator(doAssert=True)(node.left, environment).value
+        right = expressionEvaluator(doAssert=True)(node.right, environment).value
+
+        if left.type == right.type == Type.INTEGER:
+            return cls.integerEvaluator(left, node.operator, right)
+
+        if left.type == right.type == Type.STRING:
+            return cls.stringEvaluator(left, node.operator, right)
+
+        raise RuntimeException(f"Operator {node.operator.value} is not supported by {left.type.name.lower()} and {right.type.name.lower()} types", node.operator.pos)
+
+    @classmethod
+    def integerEvaluator(cls, left, operator, right):
+        if operator.value == "+":
+            return Type.integer(left.value + right.value)
+
+        if operator.value == "-":
+            return Type.integer(left.value - right.value)
+
+        raise RuntimeError("This line should never be reached")
+
+    @classmethod
+    def stringEvaluator(cls, left, operator, right):
+        if operator.value == "+":
+            return Type.string(left.value + right.value)
+
+        if operator.value == "-":
+            raise RuntimeException(f"Operator {operator.value} is not supported by string types", operator.pos)
+
+        raise RuntimeError("This line should never be reached")
\ No newline at end of file