# Definition:Length

## Disambiguation

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**Length** may refer to:

- Geometry:
- Length (Linear Measure): a formal comparison between the spatial extent of a geometric figure in a specified direction against a reference quantity (often tacitly understood).

- Analysis:
- Length of (real) interval: the difference between the endpoints of a real interval.
- Length of a curve: the limit of the length of a polygonal line inscribed within the curve as the maximum length of the chords which form that polygonal line tends to zero.

- Set Theory:
- Length of a Chain.
- Length of a Sequence: the number of terms contained in a finite sequence.

- Graph Theory:
- Length of a Walk: the number of edges in a walk (counting repeated edges as many times as they appear).
- Length of a Branch: the number of ancestors of the leaf at the end of a branch of a rooted tree.

Note that these two definitions are compatible with each other.

- Logic and Formal Systems:
- Length of a String: the number of symbols in a string.
- Length of a Tableau Proof: the number of lines in a tableau proof.

- Group Theory:
- Length of an Orbit: The number of elements contained in the orbit of an element under a group action.
- Length of a Normal Series: The number of factors in a normal series.
- Length of a Group $G$: the length of a composition series for $G$.
- Definition:Length of Cyclic Permutation