Those substance which have tendency to give oxygen is called oxidising agent.
OR
The substance which participate in a reduction is called oxidising agent.
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The substance which have tendency to gain oxygen is called reducing agent.
OR
The substance which participate in Oxidation reaction is called reducing agent
Oxidizing agents are those which oxidizes the Other compound and removes hydrogen from the compound.
Oxidizing agents are substances that gain electrons.
Examples of oxidizing agents include halogens, potassium nitrate, and nitric acid
Reducing agent isthose agent which reduces compound and themself gets oxidised..
eg. LiAlH4
Simply
the addition of oxygen to a substance and removal of hydrogen from a substsance is called oxidation reaction.
the addition of hydrogen to a substance and removal of oxygen from a substance is called reduction reaction.
for example Zno+C-Zn+Co
here Zno-substance reduced
C-substance oxidized.
C-reducing agent
Zno- oxidising agent