I'm not very familiar with the diffusion process of jujitsu, but the practice to read 術 somewhat like じつ exists(ed) in the traditional Tokyo dialect.
Japanese WP says:
This is a well-known phenomenon: //u// in Eastern dialects is generally unrounded, so a weakened //ju// could be ...
This may be a somewhat controversial, but I'm not really a fan of Sara Backer's take on the spelling. For the lay man, Ng will most likely receive the normal 'N' pronunciation with a hard 'g' sound following it (like in 'golf'). However, knowing what I do about the language, using a soft 'g' actually does get the sound phonetically written into English ...
No. ローマ字 (Roman script) is actually an alternative name for ラテン文字 (Latin script), which only refers to A, B, ..., Z. In Japanese, ローマ字 also means transcribing Japanese words using Latin alphabet, but that's an extension of the original meaning.
A, B, C, ...: Latin/Roman script ラテン文字／ローマ(文)字
0, 1, 2, ...: Arabic numeral アラビア数字
I, II, III, ...: Roman numeral ...
The history of the character's readings
Let's look at the historical and reconstructed pronunciations of 術:
Old Chinese reconstruction:
Middle Chinese reconstruction, the hypothesized source of modern Chinese dialectal readings, and Japanese and Korean borrowed readings:
To my knowledge, there is no term that specifically means "word usually written in kana". In modern standard Japanese, Western-origin loanwords are almost always written in katakana. Particles, adverbs and interjections tend to be written in hiragana. Learning words based only on kanji may not be a good idea because of this.
Pronunciation of じゅ
In Japanese, the "u" vowel /ɯ/ has a centralized allophone [ɨ] (sometimes written [ɯ̈]) when occurring after /z/ and palatalised consonants /Cj/.1 This is 'halfway between' the standard Japanese vowels /i/ and /ɯ/ (and close to the English vowel /ɪ/ in e.g. hit).
Hence じゅ is commonly realized as [d͡ʑɨ] (as opposed to [d͡ʑɯᵝ]). It may be ...
No romanization systems currently in use today use diacritics on consonants. I think it's non-intuitive to both Japanese and English speakers.
Portuguese-style romaji was used in the 16th century, and it included some diacritics. Historically, there were also French-, Dutch-, and German-style systems (see a table in the middle of this page). I don't know ...
I'm going to give a very simple answer: convention.
Korean and Chinese had systems like Hepburn, based on foreign phonology, but South Korea and China more or less decreed that a system based on native phonology rather than English approximation was to be used, and it worked in that case.
The Japanese government is softly pushing Kunrei, but not putting it'...