Merge pull request #2376 from Yash-Singh1/patch-1

Document two-way relations and fix relationship docs for class diagrams

docs/classDiagram.md

@@ -241,7 +241,7 @@ To specify the visibility of a class member (i.e. any attribute or method), thes
 A relationship is a general term covering the specific types of logical connections found on class and object diagrams.
 
 ```
-[classA][Arrow][ClassB]:LabelText
+[classA][Arrow][ClassB]
 ```
 
 There are different types of relations defined for classes under UML which are currently supported:
@@ -310,7 +310,7 @@ classM ..|> classN : Realization
 classO .. classP : Link(Dashed)
 ```
 
-## Labels on Relations
+### Labels on Relations
 
 It is possible to add a label text to a relation:
 
@@ -332,6 +332,40 @@ classE o-- classF : association
 
 ```
 
+### Two-way relations
+
+Relations can go in multiple ways:
+
+```
+classDiagram
+    Animal <|--|> Zebra
+```
+
+Here is the syntax:
+
+```
+[Relation Type][Link][Relation Type]
+```
+
+Where `Relation Type` can be one of:
+
+
+| Type | Description |
+| ---- | ----------- |
+| <\|  | Inheritance |
+| \*   | Composition |
+| o    | Aggregation |
+| >    | Association |
+| <    | Association |
+| \|>  | Realization |
+
+And `Link` can be one of:
+
+| Type | Description |
+| ---- | ----------- |
+| --   | Solid       |
+| ..   | Dashed      |
+
 ## Cardinality / Multiplicity on relations
 
 Multiplicity or cardinality in class diagrams indicates the number of instances of one class linked to one instance of the other class. For example, one company will have one or more employees, but each employee works for just one company.