---
book: 6
part: "definitions"
source: "https://scaife.perseus.org/reader/urn:cts:greekLit:tlg1799.tlg001.perseus-eng2:6"
license: "CC-BY-SA-4.0"
---

# Book VI Definitions

## Definition 1

*Similar rectilineal figures* are such as have their angles severally equal and the sides about the equal angles proportional.

## Definition 2

[*Reciprocally related* figures. *See note*.]

## Definition 3

A straight line is said to have been *cut in extreme and mean ratio* when, as the whole line is to the greater segment, so is the greater to the less.

## Definition 4

The *height* of any figure is the perpendicular drawn from the vertex to the base.

## Definition 5