a. The accusative in -im is found exclusively -
1. In Greek nouns and in names of rivers.
2. In búris, cucumis, rávis, sitis, tussis, vís.
3. In adverbs in -tim (being accusative of nouns in -tis), as, partim; and in amussim.
b. The accusative in -im is found sometimes in febris, puppis, restis turris, secúris, sémentis, and rarely in many other words.