Ooook, so the prefix "O-". If you notice, almost every word you hear in anime has that prefix on it, no? Well, I'm gonna teach this a little differently than the last 3 lessons. This time, I'll give you lists of words that don't really need this prefix, and words that really need it. If ya know what I mean. Enjoy.
Onigiri. It means rice ball, and if you take off the prefix, you'd end up with Nigiri, which is like a piece of sushi.
Obon. It can mean a japanese holiday or this tray used to carry food. Just bon would be pretty strange. In fact, any holiday with the prefix needs it.
Oden. It's a japanese food.I like it especially on cold days. Den itself would be tons of other different words.
Okama. One Piece is an exception; kama is kind of hard to understand on its own unless it is made clear.
Oyabun. Yabun means like "late at night". By the way, Okashira also means boss, but prefix is unneeded.
Terms addressing royalty. Like Ousama for instance. Usama is just plain weird. Ohimesama (princess) is an exception; Himesama is good enough.
Basically any devil fruit. Devil fruits always have 2 syllables, so the repeated word takes away unneeded letters to make it 2 syllables. Like the Ori-Ori no Mi. Ori = Cage. Ri= ?.
"I". You know, like "I am..". That I. For example, 1 way to say "I" is Ore. It wouldn't make sense w/out the prefix.
Sound effects. Like "Oraaa" is a sound people make when they're using lots of energy.
Words with double O's. Like big (Ookii).
Jobs. Like Oishyasan. (Docter)
Don't Need Prefix
Girls' names. Like you know, Nami could have the prefix to make it Onami, but it doesn't really change her name. A good instance of this would be those One Piece historical TV specials. Don't miss interpret what I said; names with O's from the very beggining need them. You know, like "Olvia" or "Oimo".
Omizu. It means water, and mizu itself is fine. In fact, any food/drink with "O-" on it. You know, like Okome for rice. Well, Onigiri and Oden are exceptions.
Oningyou. Means doll, and prefix is unneeded.
Orikoo. It means like "good kid" or something. Rikoo is the same thing, basically.
Oneesan/Oniisan. As you can see in the lesson before, prefix is uneeded. Same goes for any other way to address people that I mentioned IN FAMILY TERMS.
Formal terms. like for example, "Protect" is "Mamori" but if you're really formal, you say "Omamori". "Car" is kuruma, but people can say "Okuruma". By formal, I mean like real formal; like talking to royal people.
Animals. I think any animal. Like for example, monkey. Monkey is "saru", but some people call it "Osaru".
When people talk to babies/little kids/animals, they tend to put "O-" prefixes in front of words. Like "Suwaru" (sit) would become "Osuwari.
There's more. Like infinity. ∞. Infinity. Anyways, please feel free to ask if you want to know more about the topic. Or Japanese in general. And maybe you can give me suggestions for lessons in the future. Comments/ complaints/ ideas/ ratings/ questions/ random statements are welcome. Thanks for reading.