§47. The Latin suffix -ITUDO (> E -itude)

Although -itudo is a less productive Latin noun-forming suffix than -itas, it has exactly the same function and meaning. There appears to be no logical reason why the Latin language attached -itas to some adjectives and -itudo to others. You will easily recognize -itudo as the source of English nouns that end in -itude. Many of these have come directly from Latin, and others through French; a few are modern coinages on the analogy of those older forms. Again, the examples speak for themselves:

Sometimes this suffix could be attached to a part of speech other than an adjective. The noun servus (“slave”) gave rise to the abstract noun servitudo (“slavery”) > E servitude. There is an odd-looking Latin adverb vicissim, that means “in turn”; this produced the Latin noun vicissitudo and the wonderful English word vicissitude, which is applied to the alternating turns of human fortune. Plenitude is a learned synonym for “fullness,” and is derived regularly from Latin plenitudo < plenus (“full”). It is also the trademark for a facial cream (to get that full-fed appearance?). In later antiquity, there was a variant noun form plenitas, which is the origin of E plenty (as modified by French). A declining awareness of Latin in our own day is perhaps rendering obsolete such English words as rectitude (“uprightness”), pulchritude (“beauty”), and lassitude (“weariness”)—though teachers can still be dismissed for moral turpitude (“foulness of character”). One polysyllabic Latin derivative is still widely used and understood, however; that is the compound noun verisimilitude, from ver-i-simil-itudo (“likeness to the truth”).