# Anisotropic

**Describes a material whose properties differ by direction — in wood, movement across the grain is significant while movement along it is minimal.**

Wood does not expand and contract equally in all directions. Length change is minimal; width change is significant and cumulative across a floor. Twenty boards each moving a fraction of a millimetre becomes a visible dimension at the wall.

This is why expansion gaps run around the perimeter and around every fixed object, and why the width of a floor is where movement has to be planned for rather than the length.

## Related terms

- [Hygroscopic](https://ecowoods.ca/glossary/hygroscopic)
- [Expansion gap](https://ecowoods.ca/glossary/expansion-gap)
- [Seasonal gapping](https://ecowoods.ca/glossary/seasonal-gapping)


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- Defined in: https://ecowoods.ca/papers/toronto-hardwood-climate-moisture-protocol#climate-reality
- Citation guide: https://ecowoods.ca/ai.txt

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