Editing Suppletion (section)

===Japanese===
In modern Japanese, the copulae だ, である and です take な to create "attributive forms" of [[Adjectival noun (Japanese)|adjectival nouns]]<ref>{{cite web|url=https://kotobank.jp/word/%E5%BD%A2%E5%AE%B9%E5%8B%95%E8%A9%9E-59186#w-59186|website=Kotobank|title=形容動詞}}</ref> (hence the English moniker, "''na''-adjectives"):

{| class="wikitable"
|-
! Irrealis<br />未然形
! Adverbial<br />連用形
! Conclusive<br />終止形
! Attributive<br />連体形
! Hypothetical<br />仮定形
! Imperative<br />命令形
|-
| だろ -daro
| だっ -daQ<br />で -de<br />に -ni
| だ -da
| な -na
| なら -nara
| &nbsp;
|}

The "conclusive" and "attributive" forms, だ and な, were constructed similarly, from a combination of a [[Japanese particles|particle]] and an inflection form of the old verb あり (''ari'', "to exist").
*で + あり ("conclusive") → であり → であ → だ<ref>{{cite web|url=https://kotobank.jp/word/%E3%81%A0-556047#w-556054|website=Kotobank|title=だ}}</ref>
*に + ある ("attributive") → なる → なん → な<ref>{{cite web|url=https://kotobank.jp/word/%E3%81%AA-586863#w-2069724|website=Kotobank|title=な}}</ref>

(Note: で itself was also a contraction of earlier にて.<ref>{{cite web|url=https://kotobank.jp/word/%E3%81%A7-573220#w-2054769|website=Kotobank|title=で}}</ref>)

In modern Japanese, である ("conclusive") simply retains the older appearance of だ, while です is a different verb that can be used as a suppleted form of だ. Multiple hypotheses have been proposed for the etymology of です, one of which is a contraction of であります:<ref>{{cite web|url=https://kotobank.jp/word/%E3%81%A7%E3%81%99-575878|website=Kotobank|title=です}}</ref>
*で + あり ("adverbial") + ます → であります → です

The basic construction of the negative form of a Japanese verb is the "irrealis" form followed by ない, which would result in such hypothetical constructions as *だらない and *であらない. However, these constructions are not used in modern Japanese, and the construction ではない is used instead.<ref name=handbook>{{cite book|page=15|chapter=Verbs|title=Handbook of Modern Japanese Grammar|last=Matsuoka McClain|first=Yoko|publisher=The Hokuseido Press|location=Tokyo|year=1983|edition=6th}}</ref> This is because *あらない, the hypothetically regular negative form of ある, is not used either, and is simply replaced with ない.
*あら ("irrealis") + ない → ない
*であら ("irrealis") + ない → ではない
*だら ("irrealis") + ない → ではない → じゃない

While the auxiliary ない causes suppletion, other auxiliaries such as ん and ありません do not necessarily.
*あら ("irrealis") + ん → あらん
*あり ("adverbial") + ませ + ん → ありません
*であり ("adverbial") + ませ + ん → でありません

For です, its historical "irrealis" form, でせ has not been attested to create a negative form (only でせう → でしょう has been attested, and there were and are no *でせん and *でせない).<ref>{{cite book|page=508|title=日本語文法大辞典|last=Yamaguchi|first=Akiho|last2=秋山|first2=守英|publisher=Meiji Shoin|date=1 March 2001}}</ref> Thus, it has to borrow でありません as its negative form instead.<ref name=handbook/>

To express a potential meaning, as in "can do", most verbs use the "irrealis" form followed by れる or られる. する, notably has no such construction, and has to use a different verb for this meaning, できる.