noun. A subdivision that has common differentiating characteristics within a larger branch.

noun. A subdivision of a branch, in any sense of that word.

noun. Specifically, in zoölogical classification, a prime division of a branch or phylum; a subphylum.

noun. A branch that is itself an offshoot of a branch of something.

noun. Part of a branch.

"Living languages of the Iranian subbranch include Farsi, Tajik, and Dari all descended from Middle Persian, the language of such celebrated poets as Rumi and Hafez, as well as Kurdish, Baluchi, Pashto, and Ossetic."