What are the names of Japanese submarines in World War II: I-xx, Lu-xx, etc. What do these names mean? What does Ilu mean?

The naming of Japanese submarines in World War II followed the principle of submarine type plus number. The ship types are divided into large and small. Large submarines are prefixed with "I" (伊) in English, and small submarines are prefixed with "RO" (LV). "I" and "RO" mean the Japanese words "A" and "B". Examples: For example, Yi (I) No. 181 boat, Lu (RO) No. 55 boat, etc.