The following is a list of nouns that operates in a different grammatical gender where it appears in the plural, or features two possible genders in the plural that offer two distinct meanings.
- balneum, -ī (n) bath —> balneae (f) baths
- carbasus, -ūs (f) sail —> carbasa (n) sails
- dēlicium, -ī (n) pleasure —> dēliciae (f) pet
- epulum, -ī (n) feast —> epulae (f) feast
- frēnum, -ī (n) bit —> frēnī (m) or frēna (n) bridle (the first the more common)
- iocus, -ī (m) jest —> ioca (n) or iocī (m) jests (” “)
- locus, -ī (m) place —> loca (n) places, but locī (m) topics
- rāstrum, -ī (n) rake —> rāstrī (m) or rāstra (n) rakes (” “)
Allen and Greenough also have this entry—
- caelum, -ī (n) heaven —> caelōs (m acc.) appears in Lucretius
This is an interesting case. According to Lewis and Short, it looks like the plural of caelum is actually lacking in Classical Latin except for a passage from Lucretius. However, caelī (m) meaning ‘heavings’ is frequent in Ecclesiastical Latin. Therefore, the evidence is inconclusive as to whether the noun is truly transgender.
The Essential A & G: 106b