A **line-segment** $\overline{AB}$ is a one-dimensional [[Figure]] bounded by two [[Point|points]] $A$ and $B$
Extending past point $B$ creates **ray** $\overrightarrow{AB}$
Extending past both points $A$ and $B$ creates **line** $\overleftrightarrow{AB}$
(In most courses, a the word _line_ will mean _straight-line_, but some like Euclid interpreted [[‡ Curve|curves]] to be lines as well.)
(This a primitive which has meaning implied by its relation to [[Point]])