is a specific kind of: conifer, coniferous tree.

is a broader term that covers: Canadian hemlock, eastern hemlock, spruce pine, Tsuga canadensis | Carolina hemlock, Tsuga caroliniana | black hemlock, mountain hemlock, Tsuga mertensiana | Pacific hemlock, Tsuga heterophylla, west coast hemlock, western hemlock.

is a member of: genus Tsuga, Tsuga.

contains: hemlock.