The meaning of Erastus is Lovely and  Beloved. Its origin is Variant of the Greek name Erastos. Erastus is a form of Erastos and is generally pronounced like eh RAS tus. This name is mostly being used as a boys name. Last year it ranked 4,160th in the U.S. Social Security Administration list of most popular baby boy names.
Which undefined term is needed to define an angle? Plane Point Ray Line. Undefined, you need a line to define an angle (if you're looking for undefined terms). This is because, if you think about it, a ray is part of a line.
A line segment is a part of a line having two endpoints. A ray is a part of a line with one endpoint and goes on and on in one direction... Parallel lines are lines that never intersect or cross one another. Perpendicular lines cross each other or intersect at right angles. An angle is two lines that meet at an endpoint called a vertex. An angle can be named by the three letters that form it or by the letter that is at its vertex. An acute angle is one that measures less than 90 degrees with a protractor - that is how much the angle is open or the lines diverge from the vertex.