Clear
Clear[sym1, sym2, ...]
clears the symbol definitions from the evaluation context.
Attributes[Clear] := {HoldAll, Protected}
Simple examples
In[1]:= a Out[1]= a
In[2]:= a = 5 Out[2]= 5
In[3]:= b = 6 Out[3]= 6
In[4]:= c = 7 Out[4]= 7
In[5]:= a Out[5]= 5
In[6]:= Clear[a, 99, b] Out[6]= Null
In[7]:= Head[a] Out[7]= Symbol
In[8]:= Head[b] Out[8]= Symbol
In[9]:= Head[c] Out[9]= Integer
In[10]:= Clear[c] Out[10]= Null
In[11]:= Head[c] Out[11]= Symbol