Editing Linking number (section)

==Properties and examples==
[[Image:Labeled Whitehead Link.svg|thumb|The two curves of the [[Whitehead link]] have linking number zero.]]
* Any two unlinked curves have linking number zero.  However, two curves with linking number zero may still be linked (e.g. the [[Whitehead link]]).
* Reversing the orientation of either of the curves negates the linking number, while reversing the orientation of both curves leaves it unchanged.
* The linking number is [[chirality (mathematics)|chiral]]: taking the [[mirror image]] of link negates the linking number.  The convention for positive linking number is based on a [[right-hand rule]].
* The [[winding number]] of an oriented curve in the ''x''-''y'' plane is equal to its linking number with the ''z''-axis (thinking of the ''z''-axis as a closed curve in the [[3-sphere]]).
* More generally, if either of the curves is [[Curve#Topology|simple]], then the first [[homology (mathematics)|homology group]] of its complement is [[group isomorphism|isomorphic]] to '''[[integer|Z]]'''.  In this case, the linking number is determined by the homology class of the other curve.
* In [[physics]], the linking number is an example of a [[topological quantum number]].