Term Sima or Shima may refer to one of the following 6 Unicode characters:
㠀, 14336, X3800 
岛, 23707, X5C9B 
島, 23798, X5CF6 
嶋, 23947, X5D8B 
嶌, 23948, X5D8C 
嶹, 23993, X5DB9 
Also, term Sima may refer to the set of these six characters.
Also, Sima may be used as a generic name for an island, part of land of moderated size (bigger than a meter, but smaller than Australia), surrounded by water: ocean, sea, lake, river or swamp.
No difference is detected in pronunciation of characters of sima.
No difference is detected between meaning of characters of sima.
For these reasons, in the first approach, these characters are treated as the same.
In such a way, sima appears as class of equivalence of the Unicode characters
㠀 岛 島 嶋 嶌 嶹
In order to see them well, in the line above, these characters are enlarged.
Use of such classes of equivalence is expected to reduce the job about systematization of elements of Japanese language to 1/6 of its initial (conventional) requirements; as the basic, grammar, pronunciation and semantics are supposed to be invariant with respect to replacement of these characters within the class of equivalence.
However, the custom meaning, i.e., that is written "between lines", is lost at such a vulgarization. Therefore, after to establish the simplified grammar of Japanese language, the nuances can be added, taking into account the frequency of appearance of these characters, dependently on geographic area, on the epoch, ethnics of speakers or writers, etc. For century 21, in Japan, character 島 seems to be more usual, than other versions of sima. While we do not care about geography, nor about history, the single 3-byte character 島 can be considered as approximate of term sima. (In the similar way, in the most of usual cases, the Newtonian mechanic can be considered as a good approximation of the quantum mechanic).
php du.t 㠀岛島嶋嶌嶹
However, program du.t should be loaded; it calculates the codes of the characters, that are encoded with 3 bytes. This program seems to be sufficient for analysis of symbols of English, Japanese and some other European languages.
Characters of sima can be pronounced as "Shima" (and this gives name to the term) しま.
Characters of sima can be pronounced as "tou" , トウ.
For menemonic, one can imagine the following evolution of the sima kanji:
First, the most complicated character 嶹 had been used.
Then, due to unsufficient resolution of the printing equipment (with manual handling, before computers), the right hand side of character 嶹 happened to be not distinguishable from a little bit squeezed character tori (鳥); that leaded to character 嶋.
Indeed, with the small font, it is difficult to see difference between pictures 嶹 and 嶋.
For the improvement of perception, character yama has been moved to the upper side of the kanji, giving character 嶌.
Then, in order to see better the limits of the Kaji character, the "yama" is moved to the bottom, giving 㠀.
Then, for simplification, the four sticks at the bottom of the upper element are skipped by the lasy (and rational) writers and typiographists and, of course, the readers. Due to simplicity, character 島 becomes most usual.
Character 岛 appears as the further simplification; so, it may become dominant in century 22.
At creation of the unicode, the developers wanted to keep possibility of writing sima in all the 6 historical ways; so, all the 6 pictures of sima got their encoding and the graphical representations. These characters can be used in personal names of subjects or objects; however, at the pronunciation of the character, either the graphical representation is necessary, or the number of the Unicode character child be specified: is it X3800 or X5C9B or X5CF6 or X5D8B or X5D8C or X5DB9 ?
http://www.manythings.org/kanji/d/5cf6.htm Selected Good Words to Memorize
島 しま (n) island
半島 はんとう peninsula .. Selected Words with Definitions from WWWJDIC
島 しま island (n) ****
中島 なかじま island in a pond or river (n) **
朝鮮半島 ちょうせんはんとう Korean peninsula (n,vs) **
半島 はんとう peninsula (n) **
小島 こじま small island; islet (n) **
列島 れっとう chain of islands (n) *
島根 しまね island country (n) *
本島 ほんとう main island; this island (n)
島津 しまづ Shimadzu (n,Org); LS (n,vs)
千島 ちしま Kurile Islands (n)
- https://kanji.jitenon.jp/kanjiy/25112.html 岛 Unicode U+5C9B 部首// 山 （やま・やまへん・やまかんむり）// 画数// ７画// 音読み トウ// 訓読み しま// 意味 しま。四方が海や湖で囲まれた陸地。// 補足
- https://en.wiktionary.org/wiki/%E5%B2%9B // https://en.wiktionary.org/wiki/岛 // 岛 U+5C9B, 岛 CJK UNIFIED IDEOGRAPH-5C9B Translingual Han character 岛 (radical 46, 山+4, 7 strokes, cangjie input 心卜尸山 (PYSU), four-corner 27727) Derived characters 捣 Related characters 島 (Traditional form of 岛) 㠀 (Variant traditional form of 島 in mainland China) ..
- https://cjjc.weblio.jp/content/%E5%B2%9B https://cjjc.weblio.jp/content/岛 EDR日中対訳辞書 // 独立行政法人情報通信研究機構独立行政法人情報通信研究機構 // 岛 // 名詞 // 日本語訳島地 // 対訳の関係部分同義関係 // 岛の概念の説明 // 日本語での説明 島地[トウチ] // 島になっている土地 // 英語での説明 island // a piece of land that is an island
- https://kanji.jitenon.jp/kanjiy/14582.html 嶹の書体（明朝体）// Unicode U+5DB9// JIS水準 JIS第４水準// 部首 山 （やま・やまへん・やまかんむり）// 画数 １７画// 音読み トウ// 訓読み しま// 意味 しま。四方が海や湖で囲まれた陸地。
- https://kanji.jitenon.jp/kanjim/6083.html?getdata=5d8c&search=contain&how=%E3%81%99%E3%81%B9%E3%81%A6 https://kanji.jitenon.jp/kanjim/6083.html 嶹の書体（明朝体） Unicode U+5DB9 JIS水準 JIS第４水準 部首 山 （やま・やまへん・やまかんむり） 画数 １７画 音読み トウ 訓読み しま 意味 しま。四方が海や湖で囲まれた陸地。 補足 異体字 島 嶋 嶌 㠀 岛
- http://www.kanjidamage.com/kanji/835-island-%E5%B3%B6 http://www.kanjidamage.com/kanji/835-island-島 島 island 鳥 (bird) + 山 (mountain)