Demonstrable, a.
Etymology: [L. demonstrabilis: cf. OF. demonstrable, F. démontrable.]
1. Capable of being demonstrated; that can be proved beyond doubt or question. The grand articles of our belief are as demonstrable as geometry. Glanvill.
2. Proved; apparent. [Obs.] Shak.
Shades of meaning
Fernald has no entry of its own for demonstrable; he lists it under real.
He lists it without comment; the entries above explain its neighbors.