From systematic + -ity.
systematicity (countable and uncountable, plural systematicities)
- (now chiefly philosophy and linguistics) The state or quality of being systematic.
1845, J. L---y, “The Myths of 'Harmony'”, in The Musical World, page 291:
The coincidence in modern tongues between harmony, as spoken of sounds, with any other concordance or systematicity— is one derived from ancient Greek sources and roots […] .
2007 March 6, Andrew Sneddon, “The depths and shallows of psychological externalism”, in Philosophical Studies, volume 138, number 3, DOI:10.1007/s11098-006-9058-8:
[…] but it is reasonable to see a certain amount of causal and functional integration as a hallmark of systematicity.
2018, James Lambert, “Setting the Record Straight: An In-depth Examination of Hobson-Jobson”, in International Journal of Lexicography, volume 31, number 4, DOI:https://doi.org/10.1093/ijl/ecy010, page 491:
At times there is consistency to Yule’s headword spelling (e.g. long-a /aː/ is rendered au except when word final, where it is rendered a), but there is also inconsistency (e.g. short-a /ʌ/ is sometimes rendered a and sometimes u). My analysis indicates the lack of any overarching systematicity.