Noun
half-line (plural half-lines)
(geometry) ray; a line extending indefinitely in one direction from a point.
Any value which is negative does not lie on the ray, but rather in the opposite half-line (i.e. the one starting from with opposite direction). Source: Internet
An example of a tree diagram is the one where each of four external lines end on an X. Another is when three external lines end on an X, and the remaining half-line joins up with another X, and the remaining half-lines of this X run off to external lines. Source: Internet
Each half-line had to follow one of five or so patterns, each of which defined a sequence of stressed and unstressed syllables, typically with two stressed syllables per line. Source: Internet
The line itself should be labelled by an arrow, drawn parallel to the line, and labeled by the momentum in the line k. The half-line at the tail end of the arrow carries momentum k, while the half-line at the head-end carries momentum −k. Source: Internet
The exception is when you return to the starting point, and the final half-line must be joined with the unlinked first half-line. Source: Internet
Then form the diagram by linking the a half-line to a name and then to the other half line. Source: Internet