CCommunity
EARSUQ → SQUARE → An equally four sided geometrical shape.
ONGPOYL → POLYGON → A multiple sided geometrical shape.
NAEGRCELT → RECTANGLE → A four sided geometrical shape with two sides having equal length and other two sides having equal breadth.
RGETESNH → GREENTHS → The green growth or verdure. The greenery of anything.
Clearly, RGETESNH is not related to mathematics and is the odd one out.