Semi-infinite

In mathematics, semi-infinite objects are objects which are infinite or unbounded in some but not all possible ways.

Generally, a semi-infinite set is bounded in one direction, and unbounded in another. For instance, the natural numbers are semi-infinite considered as a subset of the integers; similarly, the intervals ${\displaystyle (c,\infty )}$ and ${\displaystyle (-\infty ,c)}$ and their closed counterparts are semi-infinite subsets of ${\displaystyle \mathbb {R} }$. Half-spaces are sometimes described as semi-infinite regions.

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