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To indicate that an expression has a definition status of 'equivalent to', three consecutive equals signs (i.e. "===") are placed at the start of the expression. For example, the following expression represents the definition of the fully defined concept

   === 46866001|Fracture of lower limb| + 428881005|Injury of tibia|:
       116676008|Associated morphology| = 72704001|Fracture|,
       363698007|Finding site| = 12611008|Bone structure of tibia|

Because expressions are most often used to represent the full definition of a clinical meaning, 'equivalent to' is the assumed definition status when it is not explicitly stated. For this reason, the expressions above has an identical meaning to the following expression:

   46866001|Fracture of lower limb| + 428881005|Injury of tibia|:
   116676008|Associated morphology| = 72704001|Fracture|,
   363698007|Finding site| = 12611008|Bone structure of tibia|

Using 'equivalent to' as the assumed definition status helps to ensure the backward compatibility of this version of compositional grammar with the previous one.

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For example, the primitive precoordinated concept

   <<< 73211009|Diabetes mellitus|: 363698007|Finding site| = 113331007|Endocrine system|

The definition status of 'subtype of' on this expression indicates that the definition is not necessarily sufficient to define the concept