I use The Kodansha Kanji Learner's Dictionary, which describes pronunciation in romaji instead of kana. I never learned romaji in a classroom, and generally only use it when reading this dictionary.
When "ō" is not proceeded by a consonant (like "tō" is), how does one know how transcribe it into kana?
I first used "おう" (such as "tō": "とう"); however, through trial and error, I came to realize that "おお" is more accurate. Then, I came across the kanji
扇 in my dictionary as "ōgi", and realized that, if I typed "おおぎ" or "おうぎ", both displayed the option of
It's quite possible this is a "spellcheck" type safeguard (the Japanese equivalent of "the" being typed out when "teh" is entered) because I have checked around various online dictionaries (Wiktionary, Yahoo!dict) and it turns out that in this case,
「おうぎ」 is indeed the correct transcription. Is there a definitive way of knowing in other cases, solely by reading the romaji?