Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
* immūtābĭlĭtas (inm-), ātis, f. [1. immutabilis], unchangeableness, immutability: in factis immutabilitatem apparere, in futuris non item, Cic. Fat. 9, 17.