Novial was created by Otto Jespersen, who had also been a co-author of Ido. Both languages base their vocabularies primarily on the Germanic and Romance languages but differ grammatically in several important respects. Comparisons among Ido, Novial, and other notable international auxiliary languages have formed an important part of interlinguistic studies. For example, both Ido and Novial were among the languages investigated by the International Auxiliary Language Association (IALA), which developed Interlingua. This article is intended to provide an overview of the salient differences and similarities of Ido and Novial.
In the Phonetic Novial spelling system (1928, 1930) the main differences between the Novial vocabulary and those of other systems come from the suppression of the letters c and z. The letter s plays an important part but tends to distort the visual appearance of some words (sientie = science, sesa = cease, sivil(i) = civil). 
The grammars of Novial and Ido differ substantially in the way that the various tenses, moods and voices of verbs are expressed. Both use a combination of auxiliary verbs and verb endings. However, Novial uses many more auxiliary verbs and few endings, while Ido uses only one auxiliary verb and a greater number of verb endings.
As with most international auxiliary languages, all verb forms in Ido and Novial are independent of person (1st, 2nd or 3rd persons) and number (singular or plural).
A PLANNED AUXILIARY LANGUAGE By Henry Jacob, 1947. A detailed comparative study of interlinguistics with full grammatical details of five systems of demonstrated usefulness, Esperanto, Ido, Occidental, Novial, and Latino sine flexione.