This is an example of transliteration rearing its ugly head. Here is an attempt to set the record straight by using standardized romaji.

Ryu (りゅ the short u sound) is a reading for Chinese hanzi that sound like liu3 or long2 (pinyin). There are three kanji with this reading:

Conversely, the kanji below sound like liu2 (pinyin) in Chinese, and have a long u sound in Japanese (りゅう), which would be more correctly ryuu (or the deprecated "u with a macron", but since The FAQ says to not use upper 128 characters, or entities, in titles, the macron should be reserved for write-ups that are contrary to the non-binding E2 Japanese Conventions):
  • ryuu 流 (style of, method of, manner of, current, flow) This kanji is used in any number of words that have a 'flowing' meme. For example ryuuboku (流 flow and 木 wood, driftwood); ryuuketsu (流 flow and 血 blood, bloodshed); ryuudoubutsu (流 flow, 動 self moving, and 物 matter, liquid); denryuu (電 warm 流 current, electricity); Also you'll see it in anything involving popularity: ryuukou- (流行 idiomatic for "going around" or fashionable). Combine it with the kanji for eye 目 you've got conjunctivitis, with speech 語 you've got buzzword, with song 歌 you've got pop song. Secondly, this kanji is used for words with the 'style' or 'school of thought or practice' meme. For example koryuu (古流 old school); and gojuryuu (剛柔流 literally "firm but gentle style", a school of karate).
  • ryuu 留 (detain, fasten, halt) This common ryuu kanji is used for words that entail being detained, or being abroad (which must be kind of like imprisonment to a Japanese). For example ryuuchi (留 detain and 置 placement, imprisonment); ryuugakusei (留 exile, 学 learning, and 生 student, student studying abroad); rusuden (留守電 an abbreviation for rusuban-denwa which is literally "house-watching telephone").
  • ryuu 硫 (sulphur) Coming from the Chinese word for sulfer it's used in compounds like sulphuric acid or hydrogen sulfide.
  • ryuu 竜 (dragon, imperial) This is the common 'spelling' for dragon, or places with dragon in their names. It is used in a few cases like ryuukotsu (竜 dragonskeleton, keel e.g. of a boat); tatsumaki (竜 dragon 巻 coil, tornado or waterspout).
  • ryuu 隆 (hump or bump, prosperous, also noble) This kanji is used in words for prosperity, swelling, and thriving (kouryuu, bouryuu, and ryuuryuu).
  • ryuu 劉 (axe, kill) This rare kanji is used for the word ryuu meaning axe, however more commonly it's fukin. You might see this kanji in the spellings of Chinese names like Liu Fang or, Liu Bei.

Since the E2 Japanese conventions promote 'short vowels' in node titles (ryu, and not ryuu), nodes like Gikan Ryu, Goju-ryu, Gyokushin Ryu, Gyokko Ryu, Kukishinden Ryu, Kumogakure Ryu, Ni Ten Ichi Ryu, Ni To Ichi Ryu, Shindenfudo Ryu, Shito Ryu, Shuri Ryu, Takagi Yoshin Ryu, Takagiyoshin Ryu, and Togakure Ryu won't need title edits. Remember the 'long u' pronunciation though, or you'll end up like the folks who call it 'kah-rah-tea' and 'carie-oakie'.