isomers which differs in position of any atom or group including c=c and carbon carbon triple bond.are called as position isomers.

e.g.  2-methylpentane.and  3-methylpentane. this is position isomers only.

isomers which differs in number of carbon atom on either side of functional group are called as metamers.

e.g. methoxy propane and ethanoxy ethane. this is metamers and also position isomers ,

metamers are always position isomers but position isomers may or may not be metamers.

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