What is it called when an orchid attaches itself to a tree branch without doing harm?

When an orchid attaches itself to a tree branch without causing harm, it is referred to as being epiphytic. Epiphytic orchids grow on the surface of the tree, using it for support and access to light and moisture, but they do not draw nutrients from the host tree. This relationship is a form of commensalism, where one organism benefits while the other is neither helped nor harmed.